While Loop Example in Java

Introduction

While Loop is a classic Java console program that demonstrates the concept with complete source code and sample output. Loops repeat work until a condition is met — essential for processing collections and numeric ranges.

This tutorial walks through the program line by line, explains how the logic works, and highlights best practices you can apply in your own code.

Definition

A while loop is a control flow statement that allows code to be executed repeatedly based on a given boolean condition. The while loop can be thought of as a repeating if statement. The while construct consists of a block of code and a condition/expression.

Syntax

while(Condition){
	//DO something
}

While Loop Example Program

class WhileLoopExample{
	public static void main(String[] args){
		int num=0;
		while(num<=5){
			System.out.println(""+num);
			num++;
		}
	}
}

Sample Output

0
1
2
3
4
5

When to use

Use this while loop example when learning or revising core Java syntax.

How it works

1. Execution begins in the main method — the JVM calls this method when you run the class.

2. int num=0; updates a variable used in the calculation or output.

3. A loop repeats the block until its condition becomes false.

4. A println / print call writes text to the console — part of the sample output below.

5. Compare your console output with the sample output for While Loop to confirm the program behaves correctly.

Best Practices

• Use meaningful variable and class names that describe their purpose.
• Compile and run the program locally — modify values to see how output changes.
• Read compiler errors carefully; they usually point to the exact line to fix.

Common Mistakes

• Copying code without understanding each line — practice by changing one statement at a time.
• Mismatching the public class name and the .java filename.
• Forgetting semicolons at the end of statements.