Java While Loops

The while loop is the loop used to run a block of code as long as certain conditions are met.

while (boolean condition) {
  // if condition is true, then execute this code block
}

Example 1: Create a while loop to print numbers from 1 to 10.

int counter=1;

while (counter<=10)
{
	System.out.print(counter+" ");
	counter++;
}

 

Output is: 1 2 3 4 5 6 7 8 9 10 

 

Example 2: Create an infinite loop with the while loop

while (true)
	System.out.print("This is an infinite loop");

or

while (true)
{
	System.out.print("This is an infinite loop");
}

 

Difference Between While Loops and Do-While Loops

Unlike while loop, do-while loop will execute the code block once without checkink the boolean condition term.  Following loops will be repeated as long as the condition is not false.

do {
  // code block
}
while (boolean condition);

 

Example 3: Create a do-while loop that continues to request numbers as long as the user continues to enter a positive number.

Scanner input = new Scanner(System.in);
int number;

do {
	System.out.println("Please write a number");
	number = input.nextInt();
}
while (number > 0);

Output:

Please write a number
> 6
Please write a number
> 10
Please write a number
> 200
Please write a number
> -1