Java While vs. Do-While Loops: The Critical Difference

Irza Hashim — Sun, 05 Jul 2026 01:16:01 +0000

In Java, both while and do-while loops repeat a block of code as long as a condition is true. However, there is one critical difference between them: when the condition is checked.

Let's look at how they work using two simple code examples.

1. The Java While Loop

A while loop checks the condition before executing the code block. If the condition is false at the very beginning, the code inside the loop will never run.

int ticketCount = 0;

while (ticketCount > 0) {
    System.out.println("Watching the movie...");
    ticketCount--;
}

Why it works:

Because ticketCount is 0, the condition ticketCount > 0 is instantly false. The computer skips the loop completely. Nothing prints on the screen.

2. The Java Do-While Loop

A do-while loop executes the code block first, and then checks the condition at the end. This means the loop will always run at least once, even if the condition is completely false.

int ticketCount = 0;

do {
    System.out.println("Trying the ride once...");
    ticketCount--;
} while (ticketCount > 0);

Why it works:

The computer enters the do block first and prints the message. Then it checks the condition ticketCount > 0. Since it is false, the loop stops.

The Output Summary

If you run both codes, your terminal output will look like this:

[While Loop Output]: (Nothing prints)

[Do-While Loop Output]:
Trying the ride once...

Key Conclusion for Beginners

Use a while loop when you want to check the condition first.
Use a do-while loop when you need the code to run at least one time, no matter what.

A Beginner's Guide to For Loops in Java

Irza Hashim — Sun, 05 Jul 2026 01:09:44 +0000

Looping is a core concept in computer science. If you need to repeat a task multiple times, you use a loop. In this short tutorial, we will learn exactly how a Java for loop works using a simple code example.

The Code Example

Here is a basic Java loop that prints a message five times:

for (int i = 0; i < 5; i++) {
    System.out.println("The value of i is: " + i);
}

How the Code Works Step-by-Step

A for loop has three main parts inside the parentheses, separated by semicolons:

int i = 0; (Initialization): This creates a counter variable named i and sets it to 0. It only runs once when the loop starts.
i < 5; (Condition): The loop checks this condition before every single run. If i is less than 5, the loop runs. If i becomes 5, the loop stops immediately.
i++ (Increment): This adds 1 to the counter variable i at the end of every loop cycle.

The Output

When you run this Java program, the computer will print this exact output on your screen:

The value of i is: 0
The value of i is: 1
The value of i is: 2
The value of i is: 3
The value of i is: 4

DEV Community: Irza Hashim

Java While vs. Do-While Loops: The Critical Difference

1. The Java While Loop

Why it works:

2. The Java Do-While Loop

Why it works:

The Output Summary

Key Conclusion for Beginners

A Beginner's Guide to For Loops in Java

The Code Example

How the Code Works Step-by-Step

The Output