Java while loop

while loop in java

While Loop in java

The  ‘while loop’ is a second type loop. It is used we are not known how many times the loop will execute. This is an entry-controlled loop. In a while loop if the initial condition is true then the execution will enter into the loop.

Syntax for the while loop

While(condition)

{

  expression 1;

  expression 2;

  expression 3;

  ---------------;

  ---------------;

}


Java While Loop


The while statement is a repetition statement. It is an entry control loop and has the following syntax :
                while ( condition ) {
                // statements
                }
The statements within the while block (between the opening and closing curly braces) are executed as long as the condition is true.
If we have only one statement, then there is no need to use the braces.
First, the condition is check. If the condition is true, then the statements are executed. Otherwise, nothing happens. After executing the statements, the condition is checked. If it is true again, the statement are executed and the condition is checked again and the process continues till the condition becomes false.
Here is an example code which prints numbers from 1 to 10.
                int i = 1;
                while (i <= 10) {
                    System.out.println(i);
                    i++;
                }
The statement i = 1 initializes with 1. The condition i <= 10 is true, so we enter the body of the loop. i is printed and incremented to 2. Now again, the condition is checked and is true. i is printed and incremented to 10. In this way, the while loop executes and prints 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. Now when i is 10, i is printed and incremented to 11. i <= 10 is false. So, control comes out of the loop.

Full Example
//To check whether a number is an Armstrong or not

import java.io.*;
public class Armstrong
{
   public static void main(String args[])throws IOException
   {
       InputStreamReader read =new InputStreamReader(System.in);
       BufferedReader in =new BufferedReader(read);
       int n, num, a, b, c,s; s=0;
       System.out.println("Enter your no.");
       n= Integer.parseInt(in.readLine());
       num=n;
       while(n>0)
       {
           a=n/10;
           b=a*10;
           c=n-b;
           s=s+c*c*c;
           n=n/10;
        }
        if(num==s)
          System.out.println("The number " +num+ " is an Armstrong no.");   
        else
         System.out.println("The number " +num+ " is not an Armstrong no.");     
}


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