March 2012 – My Programming Notes

Monthly Archives: March 2012

C++ || Stack Based Postfix Evaluation (Single Digit)

March 24, 2012 admin No comments

This page consists of another homework assignment which was presented in a C++ Data Structures course. While the previously discussed program dealt with converting Infix expressions to Postfix, this program will demonstrate exactly how to evaluate them.

NOTE: Want to convert & evaluate multi digit, decimal, and negative numbers? Click here!

REQUIRED KNOWLEDGE FOR THIS PROGRAM

What Is Postfix? How To Convert Infix To Postfix Equations Stack Data Structure Cin.getline How To Evaluate Postfix Expressions The Order Of Operations #include "ClassStackType.h"

The title of this page is called – “Stack Based Postfix Evaluation (Single Digit).” Why “single digit?” The program demonstrated on this page has the ability to evaluate a postfix equation, but it only has the ability to evaluate single digit values. What do I mean by that? Consider the infix equation: 5+2. When that expression is converted to postfix, it will come out to be: 52+, and the answer will be 7 (5+2=7). But what if we have an equation like 12+2? When that expression is converted to postfix, it will come out to be: 122+. The postfix conversion is correct, but when you try to evaluate the expression, we do not know if the math operation should be 12+2 or 1+22, it can be read either way.

Question: So why is this program being displayed if it only works for single digits?
Answer: Because it demonstrates the process of evaluating postfix equations very well.

Want to convert & evaluate multi digit, decimal, and negative numbers? Click here!

Before we get into things, here is a helpful algorithm for evaluating a postfix expression in pseudo code:





		
		
			// An algorithm for postfix evaluation.
// For example,  (1 + 2) / (5 + 6) translates to  1 2 + 5 6 + /
// which equals the result of 0.272727
// Valid operands are single digits: 0-9
// Valid operators are: +, -, *, /, ^, $
// Highest precedence: ^, $
// Lowest precedence: +,-
// the operators ')' and '('never goes on stack.

double EvaluatePostfix(string postfix)
{
  while there is input
  {
    if input is a number
        push current number on stack
    else if input is a math operator and stack is not empty
        set operand2 to the top of the operand stack
            pop the stack
        set operand1 to the top of the operand stack
            pop the stack
        apply the math operation that represents to operand1 and operand2
            push the result onto the stack
    else error
  }
  // When the loop is finished, the operand stack will contain one item,
  // the result of evaluating the expression
  pop the stack
  return the answer to the caller
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
				
						// An algorithm for postfix evaluation.
// For example,  (1 + 2) / (5 + 6) translates to  1 2 + 5 6 + /
// which equals the result of 0.272727
// Valid operands are single digits: 0-9
// Valid operators are: +, -, *, /, ^, $
// Highest precedence: ^, $
// Lowest precedence: +,-
// the operators ')' and '('never goes on stack.
 
double EvaluatePostfix(string postfix)
{
  while there is input
  {
    if input is a number
        push current number on stack
    else if input is a math operator and stack is not empty
        set operand2 to the top of the operand stack
            pop the stack
        set operand1 to the top of the operand stack
            pop the stack
        apply the math operation that represents to operand1 and operand2
            push the result onto the stack
    else error
  }
  // When the loop is finished, the operand stack will contain one item,
  // the result of evaluating the expression
  pop the stack
  return the answer to the caller
}// http://programmingnotes.org/

Once you understand the process of converting from infix to postfix, adding the ability to evaluate multiple digits within this program should be doable.

======= POSTFIX EVALUATION =======

This program uses a custom template.h class. To obtain the code for that class, click here.





		
		
			Postfix Evaluation (Single Digit)
			
C++
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 24, 2012
//    Taken From: http://programmingnotes.org/
//    File:  PostfixEvaluation.cpp
//    Description: Demonstrate the use of a stack based postfix evaluation.
// ============================================================================
#include <iostream>
#include <cstdlib>
#include <cmath>
#include "ClassStackType.h"
using namespace std;

// function prototypes
void DisplayDirections();
double EvaluatePostfix(char* postfix);
bool IsMathOperator(char token);
double DoMath(double op1, double op2, char token);

int main()
{
     // declare variables
     char expression[50]; // array holding the postfix data
     double answer = 0;

     // display directions to user
     DisplayDirections();

     // get data from user
     cout<<"\nPlease enter a postfix expression: ";
     cin.getline(expression, sizeof(expression));

     cout <<"\nThe postfix expression = "<<expression<<endl;

     cout<<"\nCalculations:\n";

     answer = EvaluatePostfix(expression);

     cout<<"\nFinal answer = "<<answer<<endl;

     return 0;
}// end of main

void DisplayDirections()
{
     cout << "\n==== Postfix Evaluation ====\n"
         <<"\nMath Operators:\n"
         <<"+ || Addition\n"
         <<"- || Subtraction\n"
         <<"* || Multiplication\n"
         <<"/ || Division\n"
         <<"% || Modulus\n"
         <<"^ || Power\n"
         <<"$ || Square Rootn\n"
         <<"Sample Postfix Equation: 45^14*232+$2-/12%24*/* \n";
}// end of DisplayDirections

double EvaluatePostfix(char* postfix)
{
    // declare function variables
    int counter = 0;
    int currentNum = 0;
    char token = 'a';
    double op1 = 0;
    double op2 = 0;
    double answer = 0;
    StackType<double> doubleStack;

    // loop thru array until there is no more data
    while(postfix[counter] != '\0')
    {
        // push numbers onto the stack
        if(isdigit(postfix[counter]))
        {
            currentNum = postfix[counter] - '0';
            doubleStack.Push(currentNum);
        }
        else if(isspace(postfix[counter]))
        {
            // DO NOTHING
        }
        // if expression is a math operator, pop numbers from stack
        // & send the popped numbers to the 'DoMath' function
        else if((IsMathOperator(postfix[counter])) && (!doubleStack.IsEmpty()))
        {
            token = postfix[counter];

            // if expression is square root operation
            // only pop stack once
            if(token == '$')
            {
                op2 = 0;
                op1 = doubleStack.Top();
                doubleStack.Pop();

                answer = DoMath(op1,op2,token);
                doubleStack.Push(answer);
            }
            else
            {
                op2 = doubleStack.Top();
                doubleStack.Pop();
                op1 = doubleStack.Top();
                doubleStack.Pop();

                answer = DoMath(op1,op2,token);
                doubleStack.Push(answer);
            }
        }
        else
        {
            cout<<"\nINVALID INPUT\n";
            exit(1);
        }
        ++counter;
    }
    // pop the final answer from the stack, and return to main
    answer = doubleStack.Top();
    doubleStack.Pop();

    return answer;
}// end of EvaluatePostfix

bool IsMathOperator(char token)
{// this function checks if operand is a math operator
     switch(token)
     {
        case '+':
            return true;
            break;
        case '-':
            return true;
            break;
        case '*':
            return true;
            break;
        case '/':
            return true;
            break;
        case '%':
            return true;
            break;
        case '^':
            return true;
            break;
        case '$':
            return true;
            break;
        default:
            return false;
            break;
     }
}// end of IsMathOperator

double DoMath(double op1, double op2, char token)
{// this function carries out the actual math process
    double ans = 0;
    switch(token)
    {
        case '+':
            cout<<op1<<token<<op2<<" = ";
            ans = op1 + op2;
            break;
        case '-':
            cout<<op1<<token<<op2<<" = ";
            ans = op1 - op2;
            break;
        case '*':
            cout<<op1<<token<<op2<<" = ";
            ans = op1 * op2;
            break;
        case '/':
            cout<<op1<<token<<op2<<" = ";
            ans = op1 / op2;
            break;
        case '%':
            cout<<op1<<token<<op2<<" = ";
            ans = (int)op1 % (int)op2;
            break;
        case '^':
            cout<<op1<<token<<op2<<" = ";
            ans = pow(op1, op2);
            break;
        case '$':
            cout<<char(251)<<op1<<" = ";
            ans = sqrt(op1);
            break;
        default:
            ans = 0;
            break;
    }
    cout<<ans<<endl;
    return ans;
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
				
						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 24, 2012
//    Taken From: http://programmingnotes.org/
//    File:  PostfixEvaluation.cpp
//    Description: Demonstrate the use of a stack based postfix evaluation.
// ============================================================================
#include <iostream>
#include <cstdlib>
#include <cmath>
#include "ClassStackType.h"
using namespace std;
 
// function prototypes
void DisplayDirections();
double EvaluatePostfix(char* postfix);
bool IsMathOperator(char token);
double DoMath(double op1, double op2, char token);
 
int main()
{
     // declare variables
     char expression[50]; // array holding the postfix data
     double answer = 0;
 
     // display directions to user
     DisplayDirections();
 
     // get data from user
     cout<<"\nPlease enter a postfix expression: ";
     cin.getline(expression, sizeof(expression));
 
     cout <<"\nThe postfix expression = "<<expression<<endl;
 
     cout<<"\nCalculations:\n";
 
     answer = EvaluatePostfix(expression);
 
     cout<<"\nFinal answer = "<<answer<<endl;
 
     return 0;
}// end of main
 
void DisplayDirections()
{
     cout << "\n==== Postfix Evaluation ====\n"
         <<"\nMath Operators:\n"
         <<"+ || Addition\n"
         <<"- || Subtraction\n"
         <<"* || Multiplication\n"
         <<"/ || Division\n"
         <<"% || Modulus\n"
         <<"^ || Power\n"
         <<"$ || Square Rootn\n"
         <<"Sample Postfix Equation: 45^14*232+$2-/12%24*/* \n";
}// end of DisplayDirections
 
double EvaluatePostfix(char* postfix)
{
    // declare function variables
    int counter = 0;
    int currentNum = 0;
    char token = 'a';
    double op1 = 0;
    double op2 = 0;
    double answer = 0;
    StackType<double> doubleStack;
 
    // loop thru array until there is no more data
    while(postfix[counter] != '\0')
    {
        // push numbers onto the stack
        if(isdigit(postfix[counter]))
        {
            currentNum = postfix[counter] - '0';
            doubleStack.Push(currentNum);
        }
        else if(isspace(postfix[counter]))
        {
            // DO NOTHING
        }
        // if expression is a math operator, pop numbers from stack
        // & send the popped numbers to the 'DoMath' function
        else if((IsMathOperator(postfix[counter])) && (!doubleStack.IsEmpty()))
        {
            token = postfix[counter];
 
            // if expression is square root operation
            // only pop stack once
            if(token == '$')
            {
                op2 = 0;
                op1 = doubleStack.Top();
                doubleStack.Pop();
 
                answer = DoMath(op1,op2,token);
                doubleStack.Push(answer);
            }
            else
            {
                op2 = doubleStack.Top();
                doubleStack.Pop();
                op1 = doubleStack.Top();
                doubleStack.Pop();
 
                answer = DoMath(op1,op2,token);
                doubleStack.Push(answer);
            }
        }
        else
        {
            cout<<"\nINVALID INPUT\n";
            exit(1);
        }
        ++counter;
    }
    // pop the final answer from the stack, and return to main
    answer = doubleStack.Top();
    doubleStack.Pop();
 
    return answer;
}// end of EvaluatePostfix
 
bool IsMathOperator(char token)
{// this function checks if operand is a math operator
     switch(token)
     {
        case '+':
            return true;
            break;
        case '-':
            return true;
            break;
        case '*':
            return true;
            break;
        case '/':
            return true;
            break;
        case '%':
            return true;
            break;
        case '^':
            return true;
            break;
        case '$':
            return true;
            break;
        default:
            return false;
            break;
     }
}// end of IsMathOperator
 
double DoMath(double op1, double op2, char token)
{// this function carries out the actual math process
    double ans = 0;
    switch(token)
    {
        case '+':
            cout<<op1<<token<<op2<<" = ";
            ans = op1 + op2;
            break;
        case '-':
            cout<<op1<<token<<op2<<" = ";
            ans = op1 - op2;
            break;
        case '*':
            cout<<op1<<token<<op2<<" = ";
            ans = op1 * op2;
            break;
        case '/':
            cout<<op1<<token<<op2<<" = ";
            ans = op1 / op2;
            break;
        case '%':
            cout<<op1<<token<<op2<<" = ";
            ans = (int)op1 % (int)op2;
            break;
        case '^':
            cout<<op1<<token<<op2<<" = ";
            ans = pow(op1, op2);
            break;
        case '$':
            cout<<char(251)<<op1<<" = ";
            ans = sqrt(op1);
            break;
        default:
            ans = 0;
            break;
    }
    cout<<ans<<endl;
    return ans;
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

Want to convert & evaluate multi digit, decimal, and negative numbers? Click here!

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output
(Note: the code was compile three separate times to display different output)

====== RUN 1 ======
==== Postfix Evaluation ==== Math Operators: + || Addition - || Subtraction * || Multiplication / || Division % || Modulus ^ || Power $ || Square Root Sample Postfix Equation: 45^14*232+$2-/12%24*/* Please enter a postfix expression: 1 2 + 5 6 + / The postfix expression = 1 2 + 5 6 + / Calculations: 1+2 = 3 5+6 = 11 3/11 = 0.272727 Final answer = 0.272727 ====== RUN 2 ====== ==== Postfix Evaluation ==== Math Operators: + || Addition - || Subtraction * || Multiplication / || Division % || Modulus ^ || Power $ || Square Root Sample Postfix Equation: 45^14*232+$2-/12%24*/* Please enter a postfix expression: 35*76^+ The postfix expression = 35*76^+ Calculations: 3*5 = 15 7^6 = 117649 15+117649 = 117664 Final answer = 117664 ====== RUN 3 ====== ==== Postfix Evaluation ==== Math Operators: + || Addition - || Subtraction * || Multiplication / || Division % || Modulus ^ || Power $ || Square Root Sample Postfix Equation: 45^14*232+$2-/12%24*/* Please enter a postfix expression: 45^4*32+$2-/12%24*/* The postfix expression = 45^4*32+$2-/12%24*/*
Calculations: 4^5 = 1024 1024*4 = 4096 3+2 = 5 √5 = 2.23607 2.23607-2 = 0.236068 4096/0.236068 = 17350.9 1%2 = 1 2*4 = 8 1/8 = 0.125 17350.9*0.125 = 2168.87 Final answer = 2168.87

C++ || Stack Based Infix To Postfix Conversion (Single Digit)

March 23, 2012 admin 4 Comments

This page consists of another homework assignment which was presented in a C++ Data Structures course. No matter which institution you attend, it seems every instructor assigns a program similar to this at one time or another.

Want to evaluate a postfix expression? Click here.

Want to convert & evaluate multi digit, decimal, and negative numbers? Click here!

REQUIRED KNOWLEDGE FOR THIS PROGRAM

What Is Infix? What Is Postfix? Stack Data Structure Cin.getline How To Convert To Postfix The Order Of Operations #include "ClassStackType.h"

The program demonstrated on this page has the ability to convert a normal infix equation to postfix equation, so for example, if the user enters the infix equation of (1*2)+3, the program will display the postfix result of 12*3+.

Before we get into things, here is a helpful algorithm for converting from infix to postfix in pseudo code:





		
		
			// An algorithm for infix to postfix expression conversion.
// For example,   a + b - c     translates to   a b + c -
//                a + b * c     translates to   a b c * +
//                (1 + 2) / (5 + 6)   goes to   1 2 + 5 6 + /
// Valid operands are single digits: 0-9, a-z, A-Z
// Valid operators are: +, -, *, /, (, ), ^, $
// Highest precedence:   ^, $
// Lowest precedence:    +,-
// ) never goes on stack.
// ( has lowest precedence on the stack and highest precedence outside of stack.
// Bottom of the stack has the lowest precedence than any operator.
// Use a prec() function to compare the precedence of the operators based on the above rules.
// Note there is little error checking in the algorithm!

void ConvertInfixToPostfix(string infix)
{
  while there is input
  {
    if input is a number or a letter
        place onto postfix string
    else
        if input is '('  // '(' has lowest precedence in the stack, highest outside
            push input on stack
        else if input is ')'
            while stack is not empty and top of stack is not '('
                place item from top of stack onto postfix string
                pop stack
            if stack is not empty // pops '(' off the stack
                pop stack
            else error  // no matching '('
        else if input is a math operator
            if stack is empty
                push input on stack
            else
                if prec(top of stack) >= prec(current math operator)
                    while stack is not empty and prec(top of stack) >= prec(current math operator)
                        place item from top of stack onto postfix string
                        pop stack
                push current math operator on stack
        else error
  }
  while stack is not empty
  {
    place item from top of stack onto postfix string
    pop stack
  }
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
				
						// An algorithm for infix to postfix expression conversion.
// For example,   a + b - c     translates to   a b + c -
//                a + b * c     translates to   a b c * +
//                (1 + 2) / (5 + 6)   goes to   1 2 + 5 6 + /
// Valid operands are single digits: 0-9, a-z, A-Z
// Valid operators are: +, -, *, /, (, ), ^, $
// Highest precedence:   ^, $
// Lowest precedence:    +,-
// ) never goes on stack.
// ( has lowest precedence on the stack and highest precedence outside of stack.
// Bottom of the stack has the lowest precedence than any operator.
// Use a prec() function to compare the precedence of the operators based on the above rules.
// Note there is little error checking in the algorithm!
 
void ConvertInfixToPostfix(string infix)
{
  while there is input
  {
    if input is a number or a letter
        place onto postfix string
    else
        if input is '('  // '(' has lowest precedence in the stack, highest outside
            push input on stack
        else if input is ')'
            while stack is not empty and top of stack is not '('
                place item from top of stack onto postfix string
                pop stack
            if stack is not empty // pops '(' off the stack
                pop stack
            else error  // no matching '('
        else if input is a math operator
            if stack is empty
                push input on stack
            else
                if prec(top of stack) >= prec(current math operator)
                    while stack is not empty and prec(top of stack) >= prec(current math operator)
                        place item from top of stack onto postfix string
                        pop stack
                push current math operator on stack
        else error
  }
  while stack is not empty
  {
    place item from top of stack onto postfix string
    pop stack
  }
}// http://programmingnotes.org/

======= INFIX TO POSTFIX CONVERSION =======

This program uses a custom template.h class. To obtain the code for that class, click here.





		
		
			Infix To Postfix Conversion (Single Digit)
			
C++
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 23, 2012
//    Taken From: http://programmingnotes.org/
//    File:  PostfixConversion.cpp
//    Description: Demonstrate the use of a stack based infix to 
//         postfix conversion.
// ============================================================================
#include <iostream>
#include <cctype>
#include <cstdlib>
#include <cstring>
#include "ClassStackType.h"
using namespace std;

// function prototypes
void DisplayDirections();
void ConvertInfixToPostfix(char* infix);
int OrderOfOperations(char token);
bool IsMathOperator(char token);

int main()
{
    // declare variables
    char expression[50]; // array holding the infix data
    
    // display directions to user
    DisplayDirections();
    
    // get data from user
    cout<<"\nPlease enter an infix expression: ";
    cin.getline(expression, sizeof(expression));
    
    cout <<"\nThe Infix expression = "<<expression<<endl;
    
    ConvertInfixToPostfix(expression);
    
    cout<<"The Postfix expression = "<<expression<<endl;
    
    return 0;
}// end of main

void DisplayDirections()
{
    cout << "\n==== Infix to Postfix Conversion ====\n"
        <<"\nMath Operators:\n"
        <<"+ || Addition\n"
        <<"- || Subtraction\n"
        <<"* || Multiplication\n"
        <<"/ || Division\n"
        <<"% || Modulus\n"
        <<"^ || Power\n"
        <<"$ || Square Root\n"
        <<"Sample Infix Equation: (((4^5)*14)/($(23+2)-2))*(1%2)/(2*4)\n";
}// end of DisplayDirections

void ConvertInfixToPostfix(char* infix)
{
    // declare function variables
    int infixCounter = 0;
    int postfixCounter = 0;
    char token = 'a';
    char postfix[50];
    StackType<char> charStack;
    
    // loop thru array until there is no more data
    while(infix[infixCounter] != '\0')
    {
        // push numbers/letters onto 'postfix' array
        if(isdigit(infix[infixCounter]) || isalpha(infix[infixCounter]))
        {
            postfix[postfixCounter] = infix[infixCounter];
            ++postfixCounter;
        }
        else if(isspace(infix[infixCounter]))
        {
            // DO NOTHING
        }
        else if(IsMathOperator(infix[infixCounter]))
        {
            // if stack is empty, place first math operator onto stack
            token = infix[infixCounter];
            if(charStack.IsEmpty())
            {
                charStack.Push(token);
            }
            else
            {
                // get the current math operator from the top of the stack
                token = charStack.Top();
                charStack.Pop(); 
                
                // use the 'OrderOfOperations' function to check equality
                // of the math operators
                while(OrderOfOperations(token) >= OrderOfOperations(infix[infixCounter]))
                {
                    // if stack is empty, do nothing
                    if(charStack.IsEmpty())
                    {
                        break;
                    }
                    // place the popped math operator from above ^
                    // onto the postfix array
                    else
                    {
                        postfix[postfixCounter] = token;
                        ++postfixCounter;
                        // pop the next operator from the stack and 
                        // continue the process until complete
                        token = charStack.Top();
                        charStack.Pop();
                    }
                }
                // push any remainding math operators onto the stack
                charStack.Push(token);
                charStack.Push(infix[infixCounter]);
            }
        }
        // push outer parentheses onto stack
        else if(infix[infixCounter] == '(')
        {
            charStack.Push(infix[infixCounter]);
        }
        else if(infix[infixCounter] == ')')
        {
            // pop the current math operator from the stack
            token = charStack.Top();
            charStack.Pop();
            while(token != '(' && !charStack.IsEmpty())
            {
                // place the math operator onto the postfix array
                postfix[postfixCounter] = token;
                ++postfixCounter; 
                // pop the next operator from the stack and
                // continue the process until complete
                token = charStack.Top();
                charStack.Pop();
            }
        }
        else
        {
            cout<<"\nINVALID INPUT\n";
            exit(1);
        }
        ++infixCounter;
    }
    
    // place any remaining math operators from the stack onto
    // the postfix array
    while(!charStack.IsEmpty())
    {
        postfix[postfixCounter] = charStack.Top();
        ++postfixCounter; 
        charStack.Pop();
    }
    
    postfix[postfixCounter] = '\0';
    // copy the data from the postfix array into the infix array
    // the data in the infix array gets sent back to main
    // since the array is passed by reference
    strcpy(infix,postfix);
}// end of ConvertInfixToPostfix

int OrderOfOperations(char token)
{// this function checks priority of each math operator
    int priority = 0;
    
    if(token == '^'|| token == '$')
    {
        priority = 4; 
    }
    else if(token == '*' || token == '/' || token == '%')
    {
        priority = 3;
    }
    else if(token == '-')
    {
        priority = 2;
    }
    else if(token == '+')
    {
        priority = 1;
    }
    return priority; 
}// end of OrderOfOperations

bool IsMathOperator(char token)
{// this function checks if operand is a math operator
     switch(token)
     {
        case '+': 
            return true;
            break;
        case '-': 
            return true;
            break;
        case '*':
            return true;
            break;
        case '/': 
            return true;
            break;
        case '%': 
            return true;
            break;
        case '^': 
            return true;
            break; 
        case '$': 
            return true;
            break;  
        default:
            return false;
            break;
     }
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
				
						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 23, 2012
//    Taken From: http://programmingnotes.org/
//    File:  PostfixConversion.cpp
//    Description: Demonstrate the use of a stack based infix to 
//         postfix conversion.
// ============================================================================
#include <iostream>
#include <cctype>
#include <cstdlib>
#include <cstring>
#include "ClassStackType.h"
using namespace std;
 
// function prototypes
void DisplayDirections();
void ConvertInfixToPostfix(char* infix);
int OrderOfOperations(char token);
bool IsMathOperator(char token);
 
int main()
{
    // declare variables
    char expression[50]; // array holding the infix data
    
    // display directions to user
    DisplayDirections();
    
    // get data from user
    cout<<"\nPlease enter an infix expression: ";
    cin.getline(expression, sizeof(expression));
    
    cout <<"\nThe Infix expression = "<<expression<<endl;
    
    ConvertInfixToPostfix(expression);
    
    cout<<"The Postfix expression = "<<expression<<endl;
    
    return 0;
}// end of main
 
void DisplayDirections()
{
    cout << "\n==== Infix to Postfix Conversion ====\n"
        <<"\nMath Operators:\n"
        <<"+ || Addition\n"
        <<"- || Subtraction\n"
        <<"* || Multiplication\n"
        <<"/ || Division\n"
        <<"% || Modulus\n"
        <<"^ || Power\n"
        <<"$ || Square Root\n"
        <<"Sample Infix Equation: (((4^5)*14)/($(23+2)-2))*(1%2)/(2*4)\n";
}// end of DisplayDirections
 
void ConvertInfixToPostfix(char* infix)
{
    // declare function variables
    int infixCounter = 0;
    int postfixCounter = 0;
    char token = 'a';
    char postfix[50];
    StackType<char> charStack;
    
    // loop thru array until there is no more data
    while(infix[infixCounter] != '\0')
    {
        // push numbers/letters onto 'postfix' array
        if(isdigit(infix[infixCounter]) || isalpha(infix[infixCounter]))
        {
            postfix[postfixCounter] = infix[infixCounter];
            ++postfixCounter;
        }
        else if(isspace(infix[infixCounter]))
        {
            // DO NOTHING
        }
        else if(IsMathOperator(infix[infixCounter]))
        {
            // if stack is empty, place first math operator onto stack
            token = infix[infixCounter];
            if(charStack.IsEmpty())
            {
                charStack.Push(token);
            }
            else
            {
                // get the current math operator from the top of the stack
                token = charStack.Top();
                charStack.Pop(); 
                
                // use the 'OrderOfOperations' function to check equality
                // of the math operators
                while(OrderOfOperations(token) >= OrderOfOperations(infix[infixCounter]))
                {
                    // if stack is empty, do nothing
                    if(charStack.IsEmpty())
                    {
                        break;
                    }
                    // place the popped math operator from above ^
                    // onto the postfix array
                    else
                    {
                        postfix[postfixCounter] = token;
                        ++postfixCounter;
                        // pop the next operator from the stack and 
                        // continue the process until complete
                        token = charStack.Top();
                        charStack.Pop();
                    }
                }
                // push any remainding math operators onto the stack
                charStack.Push(token);
                charStack.Push(infix[infixCounter]);
            }
        }
        // push outer parentheses onto stack
        else if(infix[infixCounter] == '(')
        {
            charStack.Push(infix[infixCounter]);
        }
        else if(infix[infixCounter] == ')')
        {
            // pop the current math operator from the stack
            token = charStack.Top();
            charStack.Pop();
            while(token != '(' && !charStack.IsEmpty())
            {
                // place the math operator onto the postfix array
                postfix[postfixCounter] = token;
                ++postfixCounter; 
                // pop the next operator from the stack and
                // continue the process until complete
                token = charStack.Top();
                charStack.Pop();
            }
        }
        else
        {
            cout<<"\nINVALID INPUT\n";
            exit(1);
        }
        ++infixCounter;
    }
    
    // place any remaining math operators from the stack onto
    // the postfix array
    while(!charStack.IsEmpty())
    {
        postfix[postfixCounter] = charStack.Top();
        ++postfixCounter; 
        charStack.Pop();
    }
    
    postfix[postfixCounter] = '\0';
    // copy the data from the postfix array into the infix array
    // the data in the infix array gets sent back to main
    // since the array is passed by reference
    strcpy(infix,postfix);
}// end of ConvertInfixToPostfix
 
int OrderOfOperations(char token)
{// this function checks priority of each math operator
    int priority = 0;
    
    if(token == '^'|| token == '$')
    {
        priority = 4; 
    }
    else if(token == '*' || token == '/' || token == '%')
    {
        priority = 3;
    }
    else if(token == '-')
    {
        priority = 2;
    }
    else if(token == '+')
    {
        priority = 1;
    }
    return priority; 
}// end of OrderOfOperations
 
bool IsMathOperator(char token)
{// this function checks if operand is a math operator
     switch(token)
     {
        case '+': 
            return true;
            break;
        case '-': 
            return true;
            break;
        case '*':
            return true;
            break;
        case '/': 
            return true;
            break;
        case '%': 
            return true;
            break;
        case '^': 
            return true;
            break; 
        case '$': 
            return true;
            break;  
        default:
            return false;
            break;
     }
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

Want to convert & evaluate multi digit, decimal, and negative numbers? Click here!

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Want to evaluate a postfix expression? Click here for sample code.

Once compiled, you should get this as your output
(Note: the code was compile three separate times to display different output)

====== RUN 1 ======
==== Infix to Postfix Conversion ==== Math Operators: + || Addition - || Subtraction * || Multiplication / || Division % || Modulus ^ || Power $ || Square Root Sample Infix Equation: (((4^5)*14)/($(23+2)-2))*(1%2)/(2*4) Please enter an infix expression: ((a+b)+c)/(d^e) The Infix expression = ((a+b)+c)/(d^e) The Postfix expression = ab+c+de^/ ====== RUN 2 ====== ==== Infix to Postfix Conversion ==== Math Operators: + || Addition - || Subtraction * || Multiplication / || Division % || Modulus ^ || Power $ || Square Root Sample Infix Equation: (((4^5)*14)/($(23+2)-2))*(1%2)/(2*4) Please enter an infix expression: (3*5)+(7^6) The Infix expression = (3*5)+(7^6) The Postfix expression = 35*76^+ ====== RUN 3 ====== ==== Infix to Postfix Conversion ==== Math Operators: + || Addition - || Subtraction * || Multiplication / || Division % || Modulus ^ || Power $ || Square Root Sample Infix Equation: (((4^5)*14)/($(23+2)-2))*(1%2)/(2*4)
Please enter an infix expression: (((4^5)*14)/($(23+2)-2))*(1%2)/(2*4) The Infix expression = (((4^5)*14)/($(23+2)-2))*(1%2)/(2*4) The Postfix expression = 45^14*232+$2-/12%24*/*

C++ || Snippet – Array Based Custom Template Stack Sample Code

March 22, 2012 admin No comments

This page will consist of sample code for a custom array based template stack.

REQUIRED KNOWLEDGE FOR THIS SNIPPET

Classes Template Classes - What Are They? Stacks LIFO - What Is It? #include < stack>

This template class is a custom duplication of the Standard Template Library (STL) stack class. Whether you like building your own data structures, you simply do not like to use any inbuilt functions, opting to build everything yourself, or your homework requires you make your own data structure, this sample code is really useful. I feel its beneficial building functions such as this, that way you better understand the behind the scene processes.





		
		
			#include 'ClassStackType.h'
			
C++
			
			// ============================================================================
//    Author: K Perkins
//    Date:   Mar 22, 2012
//    Taken From: http://programmingnotes.org/
//    File:  ClassStackType.h
//    Description: This is a class which implements various functions
//          demonstrating the use of a stack. 
// ============================================================================
#include <iostream>

template <class ItemType>
class StackType
{
public:
	StackType();
		/*   Function: constructor initializes class variables 
			Precondition: none
			Postcondition: defines private variables */
	bool IsEmpty();
		/*   Function: Determines whether the stack is empty
			Precondition: Stack has been initialized
			Postcondition: Function value = (stack is empty) */
	bool IsFull();
		/*   Function: Determines whether the stack is full
			Precondition: Stack has been initialized
			Postcondition: Function value = (stack is full) */
	int Size();
		/*   Function: Return the current size of the stack
			Precondition: Stack has been initialized
			Postcondition: If (stack is full) exception FullStack is thrown
							else newItem is at the top of the stack */	
	void MakeEmpty();
		/*   Function: Empties the stack
			Precondition: Stack has been initialized
			Postcondition: Stack is empty */
	void Push(ItemType newItem);
		/*   Function: Adds newItem to the top of the stack
			Precondition: Stack has been initialized
			Postcondition: If (stack is full) exception FullStack is thrown
							else newItem is at the top of the stack */
	ItemType Pop();
		/*   Function: Returns & then removes top item from the stack
			Precondition: Stack has been initialized
			Postcondition: If (stack is empty) exception EmptyStack is thrown
							else top element has been removed from the stack */
	ItemType Top();
		/*   Function: Returns the top item from the stack
			Precondition: Stack has been initialized
			Postcondition: If (stack is empty) exception EmptyStack is thrown
							else top element has been removed from the stack */
	~StackType();
		/*   Function: destructor deallocates class variables 
			Precondition: none
			Postcondition: deallocates private variables */

private:
	int top;		// indicates which element is on top
	int MAX_ITEMS;     // max number of items in the list
	ItemType stack[200];	// array holding the popped/pushed data
};

//=========================  Implementation  ================================//

template<class ItemType>
StackType<ItemType>::StackType()
{
	top = -1;
	MAX_ITEMS = 200;
}//	End of StackType

template<class ItemType>
bool StackType<ItemType>::IsEmpty()
{
	return (top == -1);
}//	End of IsEmpty

template<class ItemType>
bool StackType<ItemType>::IsFull()
{
	return (top==(MAX_ITEMS-1));
}//	End of IsFull

template<class ItemType>
int StackType<ItemType>::Size()
{
	if(IsEmpty())
	{
		std::cout<<"nSTACK EMPTYn";
		return('?');
	}
	return top+1;
}//	End of Size

template<class ItemType>
void StackType<ItemType>::MakeEmpty()
{
	top = -1;
}//	End of MakeEmpty

template<class ItemType>
void StackType<ItemType>::Push(ItemType newItem)
{
	if(IsFull())
	{
		std::cout<<"nSTACK FULLn";
		return;
	}
	stack[++top]=newItem;
}//	End of Push

template<class ItemType>
ItemType StackType<ItemType>::Pop()
{
	if(IsEmpty())
	{
		std::cout<<"nSTACK EMPTYn";
		return('?');
	}	
	return(stack[top--]);
}//	End of Pop

template<class ItemType>
ItemType StackType<ItemType>::Top()
{
	if(IsEmpty())
	{
		std::cout<<"nSTACK EMPTYn";
		return('?');
	}
	return(stack[top]);
}//	End of Top

template<class ItemType>
StackType<ItemType>::~StackType()
{
	top = -1;
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
				
						// ============================================================================
//    Author: K Perkins
//    Date:   Mar 22, 2012
//    Taken From: http://programmingnotes.org/
//    File:  ClassStackType.h
//    Description: This is a class which implements various functions
//          demonstrating the use of a stack. 
// ============================================================================
#include <iostream>
 
template <class ItemType>
class StackType
{
public:
	StackType();
		/*   Function: constructor initializes class variables 
			Precondition: none
			Postcondition: defines private variables */
	bool IsEmpty();
		/*   Function: Determines whether the stack is empty
			Precondition: Stack has been initialized
			Postcondition: Function value = (stack is empty) */
	bool IsFull();
		/*   Function: Determines whether the stack is full
			Precondition: Stack has been initialized
			Postcondition: Function value = (stack is full) */
	int Size();
		/*   Function: Return the current size of the stack
			Precondition: Stack has been initialized
			Postcondition: If (stack is full) exception FullStack is thrown
							else newItem is at the top of the stack */	
	void MakeEmpty();
		/*   Function: Empties the stack
			Precondition: Stack has been initialized
			Postcondition: Stack is empty */
	void Push(ItemType newItem);
		/*   Function: Adds newItem to the top of the stack
			Precondition: Stack has been initialized
			Postcondition: If (stack is full) exception FullStack is thrown
							else newItem is at the top of the stack */
	ItemType Pop();
		/*   Function: Returns & then removes top item from the stack
			Precondition: Stack has been initialized
			Postcondition: If (stack is empty) exception EmptyStack is thrown
							else top element has been removed from the stack */
	ItemType Top();
		/*   Function: Returns the top item from the stack
			Precondition: Stack has been initialized
			Postcondition: If (stack is empty) exception EmptyStack is thrown
							else top element has been removed from the stack */
	~StackType();
		/*   Function: destructor deallocates class variables 
			Precondition: none
			Postcondition: deallocates private variables */
 
private:
	int top;		// indicates which element is on top
	int MAX_ITEMS;     // max number of items in the list
	ItemType stack[200];	// array holding the popped/pushed data
};
 
//=========================  Implementation  ================================//
 
template<class ItemType>
StackType<ItemType>::StackType()
{
	top = -1;
	MAX_ITEMS = 200;
}//	End of StackType
 
template<class ItemType>
bool StackType<ItemType>::IsEmpty()
{
	return (top == -1);
}//	End of IsEmpty
 
template<class ItemType>
bool StackType<ItemType>::IsFull()
{
	return (top==(MAX_ITEMS-1));
}//	End of IsFull
 
template<class ItemType>
int StackType<ItemType>::Size()
{
	if(IsEmpty())
	{
		std::cout<<"nSTACK EMPTYn";
		return('?');
	}
	return top+1;
}//	End of Size
 
template<class ItemType>
void StackType<ItemType>::MakeEmpty()
{
	top = -1;
}//	End of MakeEmpty
 
template<class ItemType>
void StackType<ItemType>::Push(ItemType newItem)
{
	if(IsFull())
	{
		std::cout<<"nSTACK FULLn";
		return;
	}
	stack[++top]=newItem;
}//	End of Push
 
template<class ItemType>
ItemType StackType<ItemType>::Pop()
{
	if(IsEmpty())
	{
		std::cout<<"nSTACK EMPTYn";
		return('?');
	}	
	return(stack[top--]);
}//	End of Pop
 
template<class ItemType>
ItemType StackType<ItemType>::Top()
{
	if(IsEmpty())
	{
		std::cout<<"nSTACK EMPTYn";
		return('?');
	}
	return(stack[top]);
}//	End of Top
 
template<class ItemType>
StackType<ItemType>::~StackType()
{
	top = -1;
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

===== DEMONSTRATION HOW TO USE =====

Use of the above template class is the same as its STL counterpart. Here is a sample program demonstrating its use.





		
		
			How To Use #include 'ClassStackType.h'
			
C++
			
			#include <iostream>
#include "ClassStackType.h"
using namespace std;

int  main()
{    // declare variables
	StackType<char> charStack;
	StackType<int> intStack;
	StackType<float> floatStack;
	
	// ------ Char Example ------//
	char charArry[]="My Programming Notes";
	int counter=0;
	while(charArry[counter]!='�')
	{
		charStack.Push(charArry[counter]);
		++counter;
	}
	cout<<"charStack has "<<charStack.Size()<<" items in itn"
	<<"and contains the text: "<<charArry<<" backwards ";
	while(!charStack.IsEmpty())
	{
		cout<<charStack.Pop();
	}
	cout<<endl;	
	
	// ------ Int Example ------//
	int intArry[]={1,2,3,4,5,6,7,8,9};
	counter=0;
	while(counter<9)
	{
		intStack.Push(intArry[counter]);
		++counter;
	}
	cout<<"intStack has "<<intStack.Size()<<" items in it.n"
	<<"The sum of the numbers in the stack is: ";
	counter=0;
	while(!intStack.IsEmpty())
	{
		counter+=intStack.Pop();
	}
	cout<<counter<<endl;
	
	// ------ Float Example ------//
	float floatArry[]={1.6,2.8,3.9,4.4,5.987,6.23,7.787,8.99,9.6,1.540};
	float sum=0;
	counter=0;
	while(counter<10)
	{
		floatStack.Push(floatArry[counter]);
		++counter;
	}
	cout<<"floatStack has "<<floatStack.Size()<<" items in it.n"
	<<"The sum of the numbers in the stack is: ";
	while(!floatStack.IsEmpty())
	{
		sum+=floatStack.Pop();
	}
	cout<<sum<<endl;	
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
				
						#include <iostream>
#include "ClassStackType.h"
using namespace std;
 
int  main()
{    // declare variables
	StackType<char> charStack;
	StackType<int> intStack;
	StackType<float> floatStack;
	
	// ------ Char Example ------//
	char charArry[]="My Programming Notes";
	int counter=0;
	while(charArry[counter]!='')
	{
		charStack.Push(charArry[counter]);
		++counter;
	}
	cout<<"charStack has "<<charStack.Size()<<" items in itn"
	<<"and contains the text: "<<charArry<<" backwards ";
	while(!charStack.IsEmpty())
	{
		cout<<charStack.Pop();
	}
	cout<<endl;	
	
	// ------ Int Example ------//
	int intArry[]={1,2,3,4,5,6,7,8,9};
	counter=0;
	while(counter<9)
	{
		intStack.Push(intArry[counter]);
		++counter;
	}
	cout<<"intStack has "<<intStack.Size()<<" items in it.n"
	<<"The sum of the numbers in the stack is: ";
	counter=0;
	while(!intStack.IsEmpty())
	{
		counter+=intStack.Pop();
	}
	cout<<counter<<endl;
	
	// ------ Float Example ------//
	float floatArry[]={1.6,2.8,3.9,4.4,5.987,6.23,7.787,8.99,9.6,1.540};
	float sum=0;
	counter=0;
	while(counter<10)
	{
		floatStack.Push(floatArry[counter]);
		++counter;
	}
	cout<<"floatStack has "<<floatStack.Size()<<" items in it.n"
	<<"The sum of the numbers in the stack is: ";
	while(!floatStack.IsEmpty())
	{
		sum+=floatStack.Pop();
	}
	cout<<sum<<endl;	
}// http://programmingnotes.org/

Once compiled, you should get this as your output

charStack has 20 items in it and contains the text: My Programming Notes backwards setoN gnimmargorP yM
intStack has 9 items in it. The sum of the numbers in the stack is: 45
floatStack has 10 items in it. The sum of the numbers in the stack is: 52.834

C++ || Snippet – How To Reverse An Integer Using Modulus & While Loop

March 15, 2012 admin No comments

This page will consist of a simple program which demonstrates how to reverse an integer (not an int array) using modulus and a while loop.

REQUIRED KNOWLEDGE FOR THIS SNIPPET

Functions Modulus While Loops





		
		
			Reversing An Integer
			
C++
			
			#include <iostream>
using namespace std;

// function prototype
int ReverseNumber(int number);

int main()
{
	// declare variables
	int number = 0;
	int numReversed = 0;

	// get data from user
	cout << "Enter a number: ";
	cin >> number;

	// function call which will return the reversed number
	numReversed = ReverseNumber(number);

	// display new data to user
	cout <<endl<< number << " reversed is: "<< numReversed <<endl;

	return 0;
}// end of main

int ReverseNumber(int number)
{
	// declare function variable
	int rev=0;

	while(number > 0)
	{
		rev = rev * 10 + (number % 10);
		number = number/10;
	}

	return rev;
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
				
						#include <iostream>
using namespace std;
 
// function prototype
int ReverseNumber(int number);
 
int main()
{
	// declare variables
	int number = 0;
	int numReversed = 0;
 
	// get data from user
	cout << "Enter a number: ";
	cin >> number;
 
	// function call which will return the reversed number
	numReversed = ReverseNumber(number);
 
	// display new data to user
	cout <<endl<< number << " reversed is: "<< numReversed <<endl;
 
	return 0;
}// end of main
 
int ReverseNumber(int number)
{
	// declare function variable
	int rev=0;
 
	while(number > 0)
	{
		rev = rev * 10 + (number % 10);
		number = number/10;
	}
 
	return rev;
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output
(Note: the code was compiled three separate times to display different output)

==== RUN #1 ====
Enter a number: 2012 2012 reversed is: 2102 ==== RUN #2 ==== Enter a number: 1987 1987 reversed is: 7891 ==== RUN #3 ====
Enter a number: 241 241 reversed is: 142

Java || Using If Statements, Char & String Variables

March 05, 2012 admin 1 Comment

As previously mentioned, you can use the “int/float/double” data type to store numbers. But what if you want to store letters? Char and Strings help you do that.

===== SINGLE CHAR =====

This example will demonstrate a simple program using char, which checks to see if you entered the correctly predefined letter.





		
		
			#1 - Guess a letter
			
Java
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Jan 4, 2012
//    Updated: Mar 30, 2021
//    Taken From: http://programmingnotes.org/
//    File:  GuessALetter.java
//    Description: Demonstrates using char variables
// ============================================================================
import java.util.Scanner;

public class GuessALetter
{
    // global variable declaration
    static Scanner cin = new Scanner(System.in);

    public static void main(String[] args)
    {
        // declare variables
        char userInput = ' ';

        System.out.print("Please try to guess the letter I am thinking of: ");
        // get a single character from the user data input
        userInput = cin.next().charAt(0);

        // Use an If Statement to check equality
        if (userInput == 'a' || userInput == 'A')
        {
            System.out.println("You have Guessed correctly!");
        }
        else
        {
            System.out.println("Sorry, that was not the correct letter I was thinking of");
        }
    }// end main
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
				
						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Jan 4, 2012
//    Updated: Mar 30, 2021
//    Taken From: http://programmingnotes.org/
//    File:  GuessALetter.java
//    Description: Demonstrates using char variables
// ============================================================================
import java.util.Scanner;
 
public class GuessALetter
{
    // global variable declaration
    static Scanner cin = new Scanner(System.in);
 
    public static void main(String[] args)
    {
        // declare variables
        char userInput = ' ';
 
        System.out.print("Please try to guess the letter I am thinking of: ");
        // get a single character from the user data input
        userInput = cin.next().charAt(0);
 
        // Use an If Statement to check equality
        if (userInput == 'a' || userInput == 'A')
        {
            System.out.println("You have Guessed correctly!");
        }
        else
        {
            System.out.println("Sorry, that was not the correct letter I was thinking of");
        }
    }// end main
}// http://programmingnotes.org/

Notice in line 19 I declare the char data type, naming it “userInput.” I also initialized it as an empty variable. In line 26 I used an “If/Else Statement” to determine if the user inputted value matches the predefined letter within the program. I also used the “OR” operator in line 26 to determine if the letter the user inputted was lower or uppercase. Try compiling the program simply using this
if (userInput == 'a') as your if statement, and notice the difference.

The resulting code should give this as output

Please try to guess the letter I am thinking of: A You have Guessed correctly!

===== CHECK IF LETTER IS UPPER CASE =====

This example is similar to the previous one, and will check if a letter is uppercase





		
		
			#2 - Is Input Uppercase?
			
Java
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Jan 4, 2012
//    Updated: Mar 30, 2021
//    Taken From: http://programmingnotes.org/
//    File:  CheckIfUppercase.java
//    Description: Demonstrates checking if a char variable is uppercase
// ============================================================================
import java.util.Scanner;

public class CheckIfUppercase
{
    // global variable declaration
    static Scanner cin = new Scanner(System.in);

    public static void main(String[] args)
    {
        // declare variables
        char userInput = ' ';

        System.out.print("Please enter an UPPERCASE letter: ");
        // get a single character from the user data input
        userInput = cin.next().charAt(0);

        // Checks to see if inputted data falls between uppercase values
        if ((userInput >= 'A') && (userInput <= 'Z'))
        {
            System.out.println(userInput + " is an uppercase letter");
        }
        else
        {
            System.out.println(userInput + " is not an uppercase letter");
        }
    }// end main
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
				
						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Jan 4, 2012
//    Updated: Mar 30, 2021
//    Taken From: http://programmingnotes.org/
//    File:  CheckIfUppercase.java
//    Description: Demonstrates checking if a char variable is uppercase
// ============================================================================
import java.util.Scanner;
 
public class CheckIfUppercase
{
    // global variable declaration
    static Scanner cin = new Scanner(System.in);
 
    public static void main(String[] args)
    {
        // declare variables
        char userInput = ' ';
 
        System.out.print("Please enter an UPPERCASE letter: ");
        // get a single character from the user data input
        userInput = cin.next().charAt(0);
 
        // Checks to see if inputted data falls between uppercase values
        if ((userInput >= 'A') && (userInput <= 'Z'))
        {
            System.out.println(userInput + " is an uppercase letter");
        }
        else
        {
            System.out.println(userInput + " is not an uppercase letter");
        }
    }// end main
}// http://programmingnotes.org/

Notice in line 26, an If statement was used, which checked to see if the user inputted data fell between letter A and letter Z. We did that by using the “AND” operator. So that IF statement is basically saying (in plain english)

IF ('userInput' is equal to or greater than 'A') AND ('userInput' is equal to or less than 'Z')
THEN it is an uppercase letter

The resulting code should give this as output

Please enter an UPPERCASE letter: p p is not an uppercase letter

===== CHECK IF LETTER IS A VOWEL =====

This example will utilize more if statements, checking to see if the user inputted data is a vowel or not. This will be very similar to the previous example, utilizing the OR operator once again.





		
		
			#3 - Is Input a Vowel?
			
Java
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Jan 4, 2012
//    Updated: Mar 30, 2021
//    Taken From: http://programmingnotes.org/
//    File:  CheckIfVowel.java
//    Description: Demonstrates checking if a char variable is a vowel
// ============================================================================
import java.util.Scanner;

public class CheckIfVowel
{
    // global variable declaration
    static Scanner cin = new Scanner(System.in);

    public static void main(String[] args)
    {
        // declare variables
        char userInput = ' ';

        System.out.print("Please enter a vowel: ");
        // get a single character from the user data input
        userInput = cin.next().charAt(0);

         // Checks to see if entered data is A,E,I,O,U,Y
         if ((userInput == 'a')||(userInput == 'A')||(userInput == 'e')||
            (userInput == 'E')||(userInput == 'i')||(userInput == 'I')||
            (userInput == 'o')||(userInput == 'O')||(userInput == 'u')||
            (userInput == 'U')||(userInput == 'y')||(userInput == 'Y'))
         {
              System.out.println("Correct, " + userInput + " is a vowel!");
         }
         else
         {
              System.out.println("Sorry, " + userInput + " is not a vowel");
         }
    }// end main
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
				
						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Jan 4, 2012
//    Updated: Mar 30, 2021
//    Taken From: http://programmingnotes.org/
//    File:  CheckIfVowel.java
//    Description: Demonstrates checking if a char variable is a vowel
// ============================================================================
import java.util.Scanner;
 
public class CheckIfVowel
{
    // global variable declaration
    static Scanner cin = new Scanner(System.in);
 
    public static void main(String[] args)
    {
        // declare variables
        char userInput = ' ';
 
        System.out.print("Please enter a vowel: ");
        // get a single character from the user data input
        userInput = cin.next().charAt(0);
 
         // Checks to see if entered data is A,E,I,O,U,Y
         if ((userInput == 'a')||(userInput == 'A')||(userInput == 'e')||
            (userInput == 'E')||(userInput == 'i')||(userInput == 'I')||
            (userInput == 'o')||(userInput == 'O')||(userInput == 'u')||
            (userInput == 'U')||(userInput == 'y')||(userInput == 'Y'))
         {
              System.out.println("Correct, " + userInput + " is a vowel!");
         }
         else
         {
              System.out.println("Sorry, " + userInput + " is not a vowel");
         }
    }// end main
}// http://programmingnotes.org/

This program should be very straight forward, and its basically checking to see if the user entered data is the letter A, E, I, O, U or Y.

The resulting code should give the following output

Please enter a vowel: o Correct, o is a vowel!

===== HELLO WORLD v2 =====

This last example will demonstrate using the string data type to print the line “Hello World!” to the screen.





		
		
			#4 - Hello World - String Version
			
Java
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Jan 4, 2012
//    Updated: Mar 30, 2021
//    Taken From: http://programmingnotes.org/
//    File:  HelloWorldString.java
//    Description: Demonstrates using string variables
// ============================================================================
import java.util.Scanner;

public class HelloWorldString
{
    // global variable declaration
    static Scanner cin = new Scanner(System.in);

    public static void main(String[] args)
    {
        // declare variables
        String userInput = "";

        System.out.print("Please enter a sentence: ");
        // get a string from the user
        userInput = cin.nextLine();

        // display message to user
        System.out.println("You entered: " + userInput);
    }// end main
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
				
						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Jan 4, 2012
//    Updated: Mar 30, 2021
//    Taken From: http://programmingnotes.org/
//    File:  HelloWorldString.java
//    Description: Demonstrates using string variables
// ============================================================================
import java.util.Scanner;
 
public class HelloWorldString
{
    // global variable declaration
    static Scanner cin = new Scanner(System.in);
 
    public static void main(String[] args)
    {
        // declare variables
        String userInput = "";
 
        System.out.print("Please enter a sentence: ");
        // get a string from the user
        userInput = cin.nextLine();
 
        // display message to user
        System.out.println("You entered: " + userInput);
    }// end main
}// http://programmingnotes.org/

The resulting code should give following output

Please enter a sentence: Hello World! You entered: Hello World!

===== HOW TO COMPILE CODE USING THE TERMINAL =====

*** This can be achieved by typing the following command:
(Notice the .java source file is named exactly the same as the class header)

javac YOUR_CLASS_NAME.java

*** To run the compiled program, simply type this command:

java YOUR_CLASS_NAME

Java || Simple Math Using Int & Double

March 04, 2012 admin No comments

This page will display the use of int and double data types.

==== ADDING TWO NUMBERS TOGETHER ====

To add two numbers together, you will have to first declare your variables by doing something like this.





		
		
			#1 - Adding 2 Numbers Together
			
Java
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 4, 2012
//    Updated: Mar 7, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Add.java
//    Description: Demonstrates adding numbers together
// ============================================================================
import java.util.Scanner;

public class Add {
    public static void main(String[] args) {
        // declare variables
        int num1 = 0;
        int num2 = 0;
        int sum = 0;

        // prepare Scanner for integer data input
        Scanner cin = new Scanner(System.in);

        // get data from user
        System.out.print("Please enter the first number: ");
        num1 = cin.nextInt();

        System.out.print("Please enter the second number: ");
        num2 = cin.nextInt();

        // calculate the sum of the two numbers
        sum = num1 + num2;

        // display results to the user
        System.out.println("The sum of " + num1 + " and " + num2 + " is: " + sum);
    }// end main
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
				
						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 4, 2012
//    Updated: Mar 7, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Add.java
//    Description: Demonstrates adding numbers together
// ============================================================================
import java.util.Scanner;
 
public class Add {
    public static void main(String[] args) {
        // declare variables
        int num1 = 0;
        int num2 = 0;
        int sum = 0;
 
        // prepare Scanner for integer data input
        Scanner cin = new Scanner(System.in);
 
        // get data from user
        System.out.print("Please enter the first number: ");
        num1 = cin.nextInt();
 
        System.out.print("Please enter the second number: ");
        num2 = cin.nextInt();
 
        // calculate the sum of the two numbers
        sum = num1 + num2;
 
        // display results to the user
        System.out.println("The sum of " + num1 + " and " + num2 + " is: " + sum);
    }// end main
}// http://programmingnotes.org/

Notice in lines 14-16, I declared my variables, giving them a name. You can name your variables anything you want, with a rule of thumb as naming them something meaningful to your code (i.e avoid giving your variables arbitrary names like “x” or “y”). In line 29 the actual math process is taking place, storing the sum of “num1” and “num2” in a variable called “sum.” I also initialized my variables to zero. You should always initialize your variables.

I obtained data from the user by using the Scanner Class.

===== HOW TO COMPILE CODE USING THE TERMINAL =====

*** This can be achieved by typing the following command:
(Notice the .java source file is named exactly the same as the class header)

javac Add.java

*** To run the compiled program, simply type this command:

java Add

The above code should give you the following output:

Please enter the first number: 8 Please enter the second number: 24 The sum of 8 and 24 is: 32

==== SUBTRACTING TWO NUMBERS ====

Subtracting two ints works the same way as the above code, and we would only need to edit the above code in one place to achieve that. In line 29, replace the addition symbol with a subtraction sign, and you should have something like this





		
		
			#2 - Subtracting 2 Numbers Together
			
Java
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 4, 2012
//    Updated: Mar 7, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Subtract.java
//    Description: Demonstrates subtracting numbers together
// ============================================================================
import java.util.Scanner;

public class Subtract {
    public static void main(String[] args) {
        // declare variables
        int num1 = 0;
        double num2 = 0;
        double sum = 0;

        // prepare Scanner for integer data input
        Scanner cin = new Scanner(System.in);

        // get data from user
        System.out.print("Please enter the first number: ");
        num1 = cin.nextInt();

        System.out.print("Please enter the second number: ");
        num2 = cin.nextDouble();

        // calculate the difference of the two numbers
        sum = num1 - num2;

        // display results to the user
        System.out.println("The difference between " + num1 + " and " + num2 + " is: " + sum);
    }// end main
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
				
						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 4, 2012
//    Updated: Mar 7, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Subtract.java
//    Description: Demonstrates subtracting numbers together
// ============================================================================
import java.util.Scanner;
 
public class Subtract {
    public static void main(String[] args) {
        // declare variables
        int num1 = 0;
        double num2 = 0;
        double sum = 0;
 
        // prepare Scanner for integer data input
        Scanner cin = new Scanner(System.in);
 
        // get data from user
        System.out.print("Please enter the first number: ");
        num1 = cin.nextInt();
 
        System.out.print("Please enter the second number: ");
        num2 = cin.nextDouble();
 
        // calculate the difference of the two numbers
        sum = num1 - num2;
 
        // display results to the user
        System.out.println("The difference between " + num1 + " and " + num2 + " is: " + sum);
    }// end main
}// http://programmingnotes.org/

Note: In the above example, “cin.nextDouble()” was used on line 26 in place of “nextInt.” The declaration “nextDouble” can be used in place of “nextInt” in case you want to obtain floating point data from the user.

===== HOW TO COMPILE CODE USING THE TERMINAL =====

*** This can be achieved by typing the following command:
(Notice the .java source file is named exactly the same as the class header)

javac Subtract.java

*** To run the compiled program, simply type this command:

java Subtract

The above code should give you the following output

Please enter the first number: 8 Please enter the second number: 23.99999 The difference between 8 and 23.99999 is: -15.99999

==== MULTIPLYING TWO NUMBERS ====

This can be achieved the same way as the 2 previous methods, simply by editing line 29, and replacing the designated math operator with the star symbol “*”.





		
		
			#3 - Multiplying 2 Numbers Together
			
Java
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 4, 2012
//    Updated: Mar 7, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Multiply.java
//    Description: Demonstrates multiplying numbers together
// ============================================================================
import java.util.Scanner;

public class Multiply {
    public static void main(String[] args) {
        // declare variables
        double num1 = 0;
        int num2 = 0;
        double sum = 0;

        // prepare Scanner for integer data input
        Scanner cin = new Scanner(System.in);

        // get data from user
        System.out.print("Please enter the first number: ");
        num1 = cin.nextDouble();

        System.out.print("Please enter the second number: ");
        num2 = cin.nextInt();

        // calculate the product of the two numbers
        sum = num1 * num2;

        // display results to the user
        System.out.println("The product of " + num1 + " and " + num2 + " is: " + sum);
    }// end main
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
				
						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 4, 2012
//    Updated: Mar 7, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Multiply.java
//    Description: Demonstrates multiplying numbers together
// ============================================================================
import java.util.Scanner;
 
public class Multiply {
    public static void main(String[] args) {
        // declare variables
        double num1 = 0;
        int num2 = 0;
        double sum = 0;
 
        // prepare Scanner for integer data input
        Scanner cin = new Scanner(System.in);
 
        // get data from user
        System.out.print("Please enter the first number: ");
        num1 = cin.nextDouble();
 
        System.out.print("Please enter the second number: ");
        num2 = cin.nextInt();
 
        // calculate the product of the two numbers
        sum = num1 * num2;
 
        // display results to the user
        System.out.println("The product of " + num1 + " and " + num2 + " is: " + sum);
    }// end main
}// http://programmingnotes.org/

===== HOW TO COMPILE CODE USING THE TERMINAL =====

*** This can be achieved by typing the following command:
(Notice the .java source file is named exactly the same as the class header)

javac Multiply.java

*** To run the compiled program, simply type this command:

java Multiply

The above code should give you the following output

Please enter the first number: 7.999999 Please enter the second number: 24 The product of 7.999999 and 24 is: 191.99997

==== DIVIDING TWO NUMBERS TOGETHER ====

In division, when you divide numbers together, sometimes they end in decimals. Int data types can not store decimal data (try it yourself and see), so here is where the use of the double data type is mandatory.





		
		
			#4 - Dividing 2 Numbers Together
			
Java
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 4, 2012
//    Updated: Mar 7, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Divide.java
//    Description: Demonstrates dividing numbers together
// ============================================================================
import java.util.Scanner;

public class Divide {
    public static void main(String[] args) {
        // declare variables
        double num1 = 0;
        double num2 = 0;
        double sum = 0;

        // prepare Scanner for integer data input
        Scanner cin = new Scanner(System.in);

        // get data from user
        System.out.print("Please enter the first number: ");
        num1 = cin.nextDouble();

        System.out.print("Please enter the second number: ");
        num2 = cin.nextDouble();

        // calculate the quotient of the two numbers
        sum = num1 / num2;

        // display results to the user
        System.out.println("The quotient of " + num1 + " and " + num2 + " is: " + sum);
    }// end main
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
				
						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 4, 2012
//    Updated: Mar 7, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Divide.java
//    Description: Demonstrates dividing numbers together
// ============================================================================
import java.util.Scanner;
 
public class Divide {
    public static void main(String[] args) {
        // declare variables
        double num1 = 0;
        double num2 = 0;
        double sum = 0;
 
        // prepare Scanner for integer data input
        Scanner cin = new Scanner(System.in);
 
        // get data from user
        System.out.print("Please enter the first number: ");
        num1 = cin.nextDouble();
 
        System.out.print("Please enter the second number: ");
        num2 = cin.nextDouble();
 
        // calculate the quotient of the two numbers
        sum = num1 / num2;
 
        // display results to the user
        System.out.println("The quotient of " + num1 + " and " + num2 + " is: " + sum);
    }// end main
}// http://programmingnotes.org/

===== HOW TO COMPILE CODE USING THE TERMINAL =====

*** This can be achieved by typing the following command:
(Notice the .java source file is named exactly the same as the class header)

javac Divide.java

*** To run the compiled program, simply type this command:

java Divide

The above code should give the following output

Please enter the first number: 7.99999 Please enter the second number: 23.99999 The quotient of 7.99999 and 23.99999 is: 0.33333305

==== MODULUS ====

If you wanted to capture the remainder of the quotient you calculated from the above code, you would use the modulus operator (%).

From the above code, you would only need to edit line 29, from division, to modulus.





		
		
			#5 - Getting the Remainder of 2 Numbers
			
Java
			
			// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 4, 2012
//    Updated: Mar 7, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Modulus.java
//    Description: Demonstrates performing modulus on numbers
// ============================================================================
import java.util.Scanner;

public class Modulus {
    public static void main(String[] args) {
        // declare variables
        double num1 = 0;
        int num2 = 0;
        double remainder = 0;

        // prepare Scanner for integer data input
        Scanner cin = new Scanner(System.in);

        // get data from user
        System.out.print("Please enter the first number: ");
        num1 = cin.nextDouble();

        System.out.print("Please enter the second number: ");
        num2 = cin.nextInt();

        // calculate the remainder of the two numbers
        remainder = num1 % num2;

        // display results to the user
        System.out.println("The remainder of " + num1 + " and " + num2 + " is: " + remainder);
    }// end main
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
				
						// ============================================================================
//    Author: Kenneth Perkins
//    Date:   Mar 4, 2012
//    Updated: Mar 7, 2021
//    Taken From: http://programmingnotes.org/
//    File:  Modulus.java
//    Description: Demonstrates performing modulus on numbers
// ============================================================================
import java.util.Scanner;
 
public class Modulus {
    public static void main(String[] args) {
        // declare variables
        double num1 = 0;
        int num2 = 0;
        double remainder = 0;
 
        // prepare Scanner for integer data input
        Scanner cin = new Scanner(System.in);
 
        // get data from user
        System.out.print("Please enter the first number: ");
        num1 = cin.nextDouble();
 
        System.out.print("Please enter the second number: ");
        num2 = cin.nextInt();
 
        // calculate the remainder of the two numbers
        remainder = num1 % num2;
 
        // display results to the user
        System.out.println("The remainder of " + num1 + " and " + num2 + " is: " + remainder);
    }// end main
}// http://programmingnotes.org/

===== HOW TO COMPILE CODE USING THE TERMINAL =====

*** This can be achieved by typing the following command:
(Notice the .java source file is named exactly the same as the class header)

javac Modulus.java

*** To run the compiled program, simply type this command:

java Modulus

The above code should give the following output

Please enter the first number: 23.99999 Please enter the second number: 8 The remainder of 23.99999 and 8 is: 7.9999905

Java || Hello World!

March 04, 2012 admin No comments

This page will consist of creating the typical “hello world!” application. First, you will need to create a new project in whichever IDE you are using. I am using a simple text editor and the terminal, but any compiler will do.

When you have everything loaded up, you will start your code off by entering the headers like so into your HelloWorld.java file.





		
		
			#1 - Add Class Header
			
Java
			
			public class HelloWorld
{
    // YOUR MAIN METHOD GOES HERE
}
			
				
					
				
					1
2
3
4
				
						public class HelloWorld
{
    // YOUR MAIN METHOD GOES HERE
}

The most basic form of a class definition is shown above. The keyword “class” begins the class definition for the class named “HelloWorld.”

Next, you are going to add the main function. This will generally look something like this:





		
		
			#2 - Add main method
			
Java
			
			public static void main(String[] args) 
{
    // YOUR CODE GOES HERE
}
			
				
					
				
					1
2
3
4
				
						public static void main(String[] args) 
{
    // YOUR CODE GOES HERE
}

Every program in Java must contain a main method declaration as shown above. The declaration “public” and “static” can be written in any order (public static or static public), but the custom is to use “public static.”

We are halfway finished, now all we have to do is say hello to the world! You will do that by adding this line of code to your program, which basically outputs data to the screen





		
		
			#3 - This outputs data to screen
			
Java
			
			System.out.println("Hello World!"); 
			
				
					
				
					1
				
						System.out.println("Hello World!");

The above code uses the “System” class from the core library to print the “Hello World!” message to standard output.

So when you add everything together, your full code will look something like this





		
		
			#4 - HelloWorld.java
			
Java
			
			public class HelloWorld
{
    public static void main(String[] args) 
    {
    	// Display message to screen
        System.out.println("Hello World!"); 
    }// end of main
    
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
				
						public class HelloWorld
{
    public static void main(String[] args) 
    {
    	// Display message to screen
        System.out.println("Hello World!"); 
    }// end of main
    
}// http://programmingnotes.org/

===== HOW TO COMPILE CODE USING THE TERMINAL =====

Once you have loaded the terminal, if you have your java source file saved in any directory other than the home folder, you will need to change directories to that specific folder where your source file resides. Many typically save their source files to the desktop.

*** If your files are located on the desktop, in the terminal, type this command:

@ubuntu:~$ cd Desktop

*** Next we will compile the java source file, and this can be achieved by typing the following command:
(Notice the .java source file is named exactly the same as the class header)

@ubuntu:~/Desktop$ javac HelloWorld.java

*** To run the compiled program, simply type this command:

@ubuntu:~/Desktop$ java HelloWorld

And there you have it! After you compile the above code, you should get this as your output

Hello World!

Java || Which Compiler To Use?

March 03, 2012 admin No comments

A common question one may wonder is, which compiler should I use? There are a few choices, and your choice should probably be based on what you intend to write with it.

If you intend to program on Windows, a common choice is to download one of the many (free) Integrated Development Environment’s (IDE) which are currently available on the internet. The IDE’s I recommend are:

* NetBeans * Eclipse

Netbeans and Eclipse are the equivalent of Visual Studios and CodeBlocks for C++. (NOTE: Netbeans and Eclipse is also available for download on Linux).

You will also need to have Java installed on your computer in order to develop Java applications. If you are using Windows, then visit the Oracle website. and download and install either JDK7 or JDK7 with Netbeans. Don’t bother with JRE, as it merely runs Java programs, but does not compile them.

==== LINUX USERS ====

To install Java, open the terminal window and enter the command:

sudo apt-get install openjdk-7-jdk

If you want to add Netbeans to your computer, then use the same terminal window and enter the command below:

sudo apt-get install netbeans

Alternatively, if you want to add Eclipse to your computer, then use the same terminal window and enter the command below:

sudo apt-get install eclipse-platform

Personally, I use a simple text editor (gedit) and the terminal window in Ubuntu to program in Java, and all the source code which is presented on this site was created using that development environment.

C++ || 8 Different Ways To Reverse A String/Character Array In C++

March 01, 2012 admin 2 Comments

This page will consist of 8 different ways to reverse a character array, and a string literal (std::string).

REQUIRED KNOWLEDGE FOR THE PROGRAMS

Character Arrays String Literals Cin.getline - Use For Char Arrays Getline - Use For std::string Length Strlen Strcpy While Loops For Loops Recursion - What is it? #include < algorithm> #include < stack>

The methods on this page will be broken up into sections. This page will list:

(3) methods which reverses string literals (std::string) (4) methods which reverses character arrays (1) method which utilizes the stack to "reverse" a character sequence

Some methods listed on this page demonstrates the use of reversing a character sequence without the use of strlen/length.

======= REVERSE AN STD::STRING =======





		
		
			#1 - Reverse String Using STL Function
			
C++
			
			#include <iostream>
#include <algorithm>
#include <string>
using namespace std;

int main()
{
	// declare variable
	string name="";

	cout << "Enter your name: ";
	getline(cin,name);

	// built in C++ function to reverse an std::string
	reverse(name.begin(), name.end());
	
	cout <<"\nYour name reversed is: " <<name << endl;

	return 0;
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
				
						#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
 
int main()
{
	// declare variable
	string name="";
 
	cout << "Enter your name: ";
	getline(cin,name);
 
	// built in C++ function to reverse an std::string
	reverse(name.begin(), name.end());
	
	cout <<"\nYour name reversed is: " <<name << endl;
 
	return 0;
}// http://programmingnotes.org/

SAMPLE OUTPUT

Enter your name: My Programming Notes
Your name reversed is: setoN gnimmargorP yM





		
		
			#2 - Reverse String Recursive Method, No Length()
			
C++
			
			#include <iostream>
#include <string>
using namespace std;

// function prototypes
void Reverse(string name);

int main()
{
	// declare variable
	string name="";

	// get user data
	cout<<"Enter your name: ";
	getline(cin,name);

	cout<<"\nYour name reversed is: ";

	// function declaration
	Reverse(name);
	cout<<endl;

	return 0;
}// end of main

void Reverse(string name)
{
	if(name == "") // the base case
	{
		return;
	}
	else // the recursive step
	{
		Reverse(name.substr(1));			
		cout<<name.at(0);
	}
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
				
						#include <iostream>
#include <string>
using namespace std;
 
// function prototypes
void Reverse(string name);
 
int main()
{
	// declare variable
	string name="";
 
	// get user data
	cout<<"Enter your name: ";
	getline(cin,name);
 
	cout<<"\nYour name reversed is: ";
 
	// function declaration
	Reverse(name);
	cout<<endl;
 
	return 0;
}// end of main
 
void Reverse(string name)
{
	if(name == "") // the base case
	{
		return;
	}
	else // the recursive step
	{
		Reverse(name.substr(1));			
		cout<<name.at(0);
	}
}// http://programmingnotes.org/

SAMPLE OUTPUT

Enter your name: My Programming Notes
Your name reversed is: setoN gnimmargorP yM





		
		
			#3 - Reverse String Iterative Method, Using Length()
			
C++
			
			#include <iostream>
#include <string>
using namespace std;

// function prototypes
void Reverse(string name);

int main()
{
	// declare variable
	string name="";

	// get user data
	cout<<"Enter your name: ";
	getline(cin,name);

	cout<<"\nYour name reversed is: ";

	// function declaration
	Reverse(name);
	cout<<endl;

	return 0;
}// end of main

void Reverse(string name)
{
	// get the length of the string
	int nameLength = name.length()-1;

	while(nameLength >= 0)
	{
		cout<<name[nameLength];
		--nameLength;
	}
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
				
						#include <iostream>
#include <string>
using namespace std;
 
// function prototypes
void Reverse(string name);
 
int main()
{
	// declare variable
	string name="";
 
	// get user data
	cout<<"Enter your name: ";
	getline(cin,name);
 
	cout<<"\nYour name reversed is: ";
 
	// function declaration
	Reverse(name);
	cout<<endl;
 
	return 0;
}// end of main
 
void Reverse(string name)
{
	// get the length of the string
	int nameLength = name.length()-1;
 
	while(nameLength >= 0)
	{
		cout<<name[nameLength];
		--nameLength;
	}
}// http://programmingnotes.org/

SAMPLE OUTPUT

Enter your name: My Programming Notes
Your name reversed is: setoN gnimmargorP yM

======= REVERSE A CHARACTER ARRAY =======

The following will demonstrate (4) methods which reverses a character array.





		
		
			#4 - Reverse Char Array Recursive Method, No Strlen
			
C++
			
			#include <iostream>
using namespace std;

// function prototype
void Reverse(char name[]);

int main()
{
	// declare variable
	char name[30];

	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));

	cout<<"\nYour name reversed is: ";

	// function declaration
	Reverse(name);
	cout<<endl;

	return 0;
}// end of main

void Reverse(char name[])
{
	if(*name=='\0') // the base case
	{
		return;
	}
	else // the recursive step
	{
		Reverse(name+1);
		cout<<*(name);
	}
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
				
						#include <iostream>
using namespace std;
 
// function prototype
void Reverse(char name[]);
 
int main()
{
	// declare variable
	char name[30];
 
	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));
 
	cout<<"\nYour name reversed is: ";
 
	// function declaration
	Reverse(name);
	cout<<endl;
 
	return 0;
}// end of main
 
void Reverse(char name[])
{
	if(*name=='\0') // the base case
	{
		return;
	}
	else // the recursive step
	{
		Reverse(name+1);
		cout<<*(name);
	}
}// http://programmingnotes.org/

SAMPLE OUTPUT

Enter your name: My Programming Notes
Your name reversed is: setoN gnimmargorP yM





		
		
			#5 - Reverse Char Array Iterative Method, No Strlen
			
C++
			
			#include <iostream>
using namespace std;

// function prototypes
void Reverse(char name[]);

int main()
{
	// declare variable
	char name[30];

	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));

	cout<<"\nYour name reversed is: ";

	// function declaration
	Reverse(name);
	cout<<endl;

	return 0;
}// end of main

void Reverse(char name[])
{
	int nameLength = 0;

	//get the length of array
	while(name[nameLength] != '\0')
	{
		++nameLength;
	}

	//decrease the length of by 1
	--nameLength;

	// display reversed string
	while(nameLength >= 0)
	{
		cout<<name[nameLength];
		--nameLength;
	}
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
				
						#include <iostream>
using namespace std;
 
// function prototypes
void Reverse(char name[]);
 
int main()
{
	// declare variable
	char name[30];
 
	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));
 
	cout<<"\nYour name reversed is: ";
 
	// function declaration
	Reverse(name);
	cout<<endl;
 
	return 0;
}// end of main
 
void Reverse(char name[])
{
	int nameLength = 0;
 
	//get the length of array
	while(name[nameLength] != '\0')
	{
		++nameLength;
	}
 
	//decrease the length of by 1
	--nameLength;
 
	// display reversed string
	while(nameLength >= 0)
	{
		cout<<name[nameLength];
		--nameLength;
	}
}// http://programmingnotes.org/

SAMPLE OUTPUT

Enter your name: My Programming Notes
Your name reversed is: setoN gnimmargorP yM





		
		
			#6 - Reverse Char Array Iterative Method, No Strlen
			
C++
			
			#include <iostream>
#include <cstring>
using namespace std;

// function prototypes
void Reverse(char name[]);

int main()
{
	// declare variable
	char name[30];

	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));

	// function declaration
	Reverse(name);

	cout<<"\nYour name reversed is: "<< name<<endl;

	return 0;
}// end of main

void Reverse(char name[])
{
	// private variables
	int nameLength = 0;
	char copy[30];

	strcpy(copy,name);

	//get lenght of array
	while(name[nameLength] != '\0')
	{
		++nameLength;
	}

	//decrease the length of by 1
	--nameLength;

	// reverse the array
	for(int x = 0; x <= nameLength; ++x)
	{
		// rearange the order of the two arrays
		name[nameLength - x] = copy[x];
	}	
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
				
						#include <iostream>
#include <cstring>
using namespace std;
 
// function prototypes
void Reverse(char name[]);
 
int main()
{
	// declare variable
	char name[30];
 
	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));
 
	// function declaration
	Reverse(name);
 
	cout<<"\nYour name reversed is: "<< name<<endl;
 
	return 0;
}// end of main
 
void Reverse(char name[])
{
	// private variables
	int nameLength = 0;
	char copy[30];
 
	strcpy(copy,name);
 
	//get lenght of array
	while(name[nameLength] != '\0')
	{
		++nameLength;
	}
 
	//decrease the length of by 1
	--nameLength;
 
	// reverse the array
	for(int x = 0; x <= nameLength; ++x)
	{
		// rearange the order of the two arrays
		name[nameLength - x] = copy[x];
	}	
}// http://programmingnotes.org/

SAMPLE OUTPUT

Enter your name: My Programming Notes
Your name reversed is: setoN gnimmargorP yM





		
		
			#7 - Reverse Char Array Iterative Method, Using Strlen
			
C++
			
			#include <iostream>
#include <cstring>
using namespace std;

// function prototypes
void Reverse(char name[]);

int main()
{
	// declare variable
	char name[30];

	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));

	// function declaration
	Reverse(name);

	cout<<"\nYour name reversed is: "<< name<<endl;

	return 0;
}// end of main

void Reverse(char name[])
{
	// get the length of the current word in the array index
	int nameLength = strlen(name)-1;
	
	// increment thru each letter within the current char array index
	// reversing the order of the array
	for(int currentChar=0; currentChar < nameLength; --nameLength, ++currentChar)
	{
		// copy 1st letter in the array index into temp
		char temp = name[currentChar]; 
		// copy last letter in the array index into the 1st array index
		name[currentChar] = name[nameLength];
		// copy temp into last array index
		name[nameLength] = temp;
	}
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
				
						#include <iostream>
#include <cstring>
using namespace std;
 
// function prototypes
void Reverse(char name[]);
 
int main()
{
	// declare variable
	char name[30];
 
	// get user data
	cout<<"Enter your name: ";
	cin.getline(name, sizeof(name));
 
	// function declaration
	Reverse(name);
 
	cout<<"\nYour name reversed is: "<< name<<endl;
 
	return 0;
}// end of main
 
void Reverse(char name[])
{
	// get the length of the current word in the array index
	int nameLength = strlen(name)-1;
	
	// increment thru each letter within the current char array index
	// reversing the order of the array
	for(int currentChar=0; currentChar < nameLength; --nameLength, ++currentChar)
	{
		// copy 1st letter in the array index into temp
		char temp = name[currentChar]; 
		// copy last letter in the array index into the 1st array index
		name[currentChar] = name[nameLength];
		// copy temp into last array index
		name[nameLength] = temp;
	}
}// http://programmingnotes.org/

SAMPLE OUTPUT

Enter your name: My Programming Notes
Your name reversed is: setoN gnimmargorP yM

======= REVERSE A CHARACTER SEQUENCE USING A STACK =======

The following will demonstrate (1) method which reverses a character sequence using the STL stack.





		
		
			#8 - Reverse Char Sequence Using Stack
			
C++
			
			#include <iostream>
#include <stack>
using namespace std;

// function prototypes
void Reverse(stack<char> &name);

int main()
{ 
	// using the internal system stack
	stack<char> name;
	char singleChar;
	
	cout<<"Enter your name: ";
	
	while(cin.get(singleChar) && singleChar != '\n')
	{
		name.push(singleChar);
	}
	
	cout<<"\nYour name reversed is: ";

	// function declaration
	Reverse(name);
	cout<<endl;

	return 0;
}// end of main

void Reverse(stack<char> &name)
{
	while(!name.empty())
	{
		cout << name.top();
		name.pop();
	}
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
				
						#include <iostream>
#include <stack>
using namespace std;
 
// function prototypes
void Reverse(stack<char> &name);
 
int main()
{ 
	// using the internal system stack
	stack<char> name;
	char singleChar;
	
	cout<<"Enter your name: ";
	
	while(cin.get(singleChar) && singleChar != '\n')
	{
		name.push(singleChar);
	}
	
	cout<<"\nYour name reversed is: ";
 
	// function declaration
	Reverse(name);
	cout<<endl;
 
	return 0;
}// end of main
 
void Reverse(stack<char> &name)
{
	while(!name.empty())
	{
		cout << name.top();
		name.pop();
	}
}// http://programmingnotes.org/

SAMPLE OUTPUT

Enter your name: My Programming Notes
Your name reversed is: setoN gnimmargorP yM

Monthly Archives: March 2012

C++ || Stack Based Postfix Evaluation (Single Digit)

C++ || Stack Based Infix To Postfix Conversion (Single Digit)

C++ || Snippet – Array Based Custom Template Stack Sample Code

C++ || Snippet – How To Reverse An Integer Using Modulus & While Loop

Java || Using If Statements, Char & String Variables

Java || Simple Math Using Int & Double

Java || Hello World!

Java || Which Compiler To Use?

C++ || 8 Different Ways To Reverse A String/Character Array In C++

Search

Compile Your Code Now

Translate Page

Popular Pages

Recent

Archives

Categories