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 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);
	}
}

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 the program is executed in the terminal. If you execute the 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 a do-while loop is when you want to execute the statements inside the loop at least once, even though condition expression returns false. Otherwise, it’s always better to use a while loop. Java while loop looks cleaner than a 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