Java While Loop

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The test expression inside parenthesis is a boolean expression.

Loop is used in programming to repeat a specific block of code. In this article, you will learn to create while and do...while loops in Java programming.

Loop is used in programming to repeat a specific block of code until certain condition is met (test expression is false).

Loops are what makes computers interesting machines. Imagine you need to print a sentence 50 times on your screen. Well, you can do it by using print statement 50 times (without using loops). How about you need to print a sentence one million times? You need to use loops.

It's just a simple example. You will learn to use while and do..while loop to write some interesting programs in this article.

If the test expression is evaluated to true,
  • statements inside the while loop are executed.
  • then, the test expression is evaluated again.

This process goes on until the test expression is evaluated to false.

If the test expression is evaluated to false,

  • while loop is terminated.
Syntax:
while(condition) { //code to be executed }
Flowchart of while Loop
flowchart of java while loop
Example:
Write a program in Java to display n terms of natural numbers

public class WhileExample 
{  
public static void main(String[] args) 
    {  
    int i=1;  
    System.out.println("Display 10 Natural numbers:");  
    while(i<=10)
    {  
        System.out.println(i);  
    i++;  
    }  
}  
}


Output:

Display 10 Natural numbers:

1
2
3
4
5
6
7
8
9
10
Write a program in Java to display n terms of natural numbers

import java.util.Scanner;
public class WhileExample 
 {  
public static void main(String[] args) 
 {  
    int i=1,n;  
 Scanner p=new Scanner(System.in);
 System.out.println("Enter any value:");
 n=p.nextInt();
 System.out.println("Display "+n+" natural numbers");
    while(i<=n)
 {  
        System.out.println(i);  
    i++;  
    }  
}  
}


Output:

Enter any value:
20
Display 20 natural numbers
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Write a program in Java to display the n terms of even natural number

import java.util.Scanner;
public class WhileExample 
 {  
public static void main(String[] args) 
 {  
    int i=1,n;  
 Scanner p=new Scanner(System.in);
 System.out.println("Enter any value:");
 n=p.nextInt();
 System.out.println("Display "+n+" natural numbers");
    while(i<=n)
 {  
  if(i%2==0)
  {
        System.out.println(i);  
  }
    i++;  
    }  
}  
}


Output:

Enter any value:
30
Display 30 natural numbers
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
Java Infinitive While Loop

If you pass true in the while loop, it will be infinitive while loop.

Syntax:

while(true)
{  
//code to be executed  
}  


public class WhileExample2 
{  
public static void main(String[] args) 
{  
    while(true)
   {  
        System.out.println("infinitive while loop");  
    }  
}  
}


Output:

infinitive while loop
infinitive while loop
infinitive while loop
infinitive while loop
infinitive while loop
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