do while loop in java

Let’s learn do while loop in java.

do while loop in java

In do while loop code block is executed at least once and then condition is checked. do while loop executes the statements and then evaluates the condition of loop’s body until given condition is true.

So do while loop is guaranteed to execute the body at least once. Here expression in do while loop should return a boolean value.

Here’s do while syntax java.

do{
   statement(s);
}while(condition);

Here’s the do while loop syntax we have got the do keyword and right after the keyword we have code block the left and right curly braces.

After the code block there’s while keyword and then condition in parentheses and then a semicolon at the end. Semicolon is required for do while.

In do while loop condition is at the bottom so the code executes once in the code block and then the condition is checked.


Flow diagram of do while loop

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.

Here’s do while java program.

public class DoWhileLoopExample
{
   public static void main(String[] args)
   {
      int a = 5;
      do {
          System.out.print(a);
          a++;
          System.out.print("\n");
      }while(a < 10);
   }
}

Output:

5
6
7
8
9


do while Infinite loop

An infinite do while loop is a loop that will execute endlessly because loop’s expression is always true. Here’s do while infinite 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 using do-while loop. Let’s see an example on iterating an array using do-while loop.

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

Output:

2
4
6
8


Write a program to display number 1 to 50 using do while loop in java

Let’s learn to write a program to display number 1 to 50 using do while loop in java.

import java.util.Scanner;
public class ProgramDisplayNumber 
{
   public static void main(String[] args) 
   {
      int counter;
      int number;
      Scanner sc = new Scanner(System.in);
      System.out.println("Please enter maximum number: ");
      number = sc.nextInt();
      counter = 1;
      do{
          System.out.println(counter + " ");
          counter++;
      }while(counter <= number);
      sc.close();
   }
}

Output:

Please enter maximum number: 50
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


Also read – java overview

Click here to learn difference between while and do while loop in java.