Do-while loop in java

In this post we are going to learn do-while loop in java.

Do-while loop in java

Do while loop java executes the statements and then evaluates the expression/condition of loop’s body until given condition is true.

So do while java is guaranteed to execute the body at least once.¬†Here expression in do while loop in java should return boolean value. Here’s syntax of do while loop in java,

// do while loop java
do
{
   statement(s);
}
while(expression/condition);

How does do while java work?

do-while loop in java

In the above flow diagram first statements inside loop execute then condition gets evaluated. If condition is true then control gets shifted inside “do” else jumps outside loop.

Also read – continue statement in java

Here’s java do while loop example,

public class DoWhileDemo
{
   public static void main(String[] args)
   {
      int x = 1;
      do
      {
         System.out.println(x);
         x++;
      }
      while(x <= 5);
   }
}

Output:

1
2
3
4
5

Infinite loop

An infinite do while loop is a loop that will execute endlessly because loop’s expression is always true. Here’s java do while loop example,

public class InfiniteDoWhileDemo 
{
   public static void main(String[] args) throws InterruptedException
   {
      do
      { 
         System.out.println("Start do while");
         System.out.println("End do while");
         Thread.sleep(3 * 1000);
      }while(true);  // press ctrl+c to exit 
   }
}

Similarly we can iterate an array. Let’s see an example of do while loop in java,

class DoWhileLoopDemo 
{
   public static void main(String args[])
   {
      int arrNum[] = {2,4,6,8};
      int a = 0;
      do
      {
         System.out.println(arr[a]);
         a++;
      }while(a < 4);
   }
}

Output:

2
4
6
8