Java do while loop

Filed Under: Java

Java do while loop is used to execute a block of statements continuously until the given condition is true. do while loop in Java is similar to while loop except that the condition is checked after the statements are executed, so do while loop guarantees the loop execution at least once.

Java do while loop

Java do while loop syntax is as follows:


do {
     // statements
} while (expression);

The expression for the do-while loop must return a boolean value, otherwise, it will throw compile time error.

do while java flow diagram

Java Do While Loop

Java Do While Loop

Java do while loop example

Here is a simple java do while loop example to print numbers from 5 to 10.


package com.journaldev.javadowhileloop;

public class JavaDoWhileLoop {

	public static void main(String[] args) {

		int i = 5;
		do {
			System.out.println(i);
			i++;
		} while (i <= 10);
	}
}

java do while loop example

do while true java

We can create an infinite loop by passing boolean expression as true in the do while loop.

Here is a simple do while java infinite loop example.


package com.journaldev.javadowhileloop;

public class DoWhileTrueJava {

	public static void main(String[] args) throws InterruptedException {
		do {
			System.out.println("Start Processing inside do while loop");
			// look for a file at specific directory
			// if found, then process it, such as inserting rows into database
			System.out.println("End Processing of do while loop");

			Thread.sleep(5 * 1000);
		} while (true);
	}
}

Note that you will have to manually quit the application to stop it, using Ctrl+C if program is executed in terminal. If you have executed program in Eclipse IDE then there is a red color button to terminate the program.

do while vs while loop

The only time you should use do while loop is when you want to execute the statements inside loop at least once, even though condition expression returns false. Otherwise it’s always better to use while loop.

Java while loop looks more cleaner than do while loop.

That’s all for java do while loop. You should also look into java for loop and java continue statement.

Reference: Oracle Documentation

Comments

  1. rupesh says:

    please give syntax for do while loop

  2. Nikhil says:

    hi Pankaj,

    Can you please correct the “if condition is true arrow” in the image?

    1. Pankaj says:

      Ah, thanks for noticing that small mistake. I have corrected the image now.

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