What is a while loop in Java?

Kate 18 Published: 09/09/2024

What is a while loop in Java?

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difference between while and do-while loop in java

The age-old question: what's the difference between while and do-while loops in Java?

In Java, both while and do-while are control flow statements that allow you to execute a block of code repeatedly based on a condition. The main difference between them lies in when they check the condition.

While Loop

A while loop checks the condition before executing the block of code. Here's the syntax:

while (condition) {
// code to be executed
}

The flow is as follows:

Check the condition. If true, execute the code inside the loop. Repeat step 1.

For example:

int i = 0;
while (i < 5) {
System.out.println("Hello!");
i++;
}

This will print "Hello!" five times.

Do-While Loop

A do-while loop, on the other hand, executes the code block at least once before checking the condition. Here's the syntax:

do {
// code to be executed
} while (condition);

The flow is as follows:

Execute the code inside the loop. Check the condition. If true, repeat step 1.

Here's an example:

int i = 0;
do {
System.out.println("Hello!");
i++;
} while (i < 5);

This will also print "Hello!" five times.

Key differences

So, what are the main differences between while and do-while?

Order of execution: In a while loop, the condition is checked before executing the code. In a do-while loop, the code is executed at least once before checking the condition. Minimum iteration: A while loop might never execute if the initial condition is false. A do-while loop always executes the code block at least once.

When to use each?

Use a while loop when you need to perform some action repeatedly based on a condition, and you want to ensure that the condition is met before performing the action. Use a do-while loop when you want to execute a block of code at least once, regardless of the condition. This is useful for situations where you need to perform some setup or initialization before checking the condition.

In summary, both while and do-while loops are used to repeat a block of code, but they differ in their order of execution and minimum iteration requirements. Choose wisely!