Infinite Loop in Java

Infinite loop in java refers to a situation where a condition is setup so that your loop continues infinitely without a stop. A loop statement is used to iterate statements or expressions for a definite number of times but sometimes we may need to iterate not for a fixed number but infinitely. For such situations, we need infinite loops in java. There are basically three looping structures in java: for, while and do while.

These structures are used for iterations i.e., these statements can allow the repetition of a set of statements or functions. While using them for infinite repetitions, we may use the following ways.

The syntax of a for loop goes like this:

for(variable_initialization ; condition ; updation)
{
	//set of statement(s)/ expressions to be repeated .
}

Example:

for(int i=0; i<2; i++)
{
	System.out.println("Hello World");
}

It will print:

Hello World

Now, if we want to make our for loop go infinitely, we can try the following ways:

class example
{
	public static void main(String args[])
	{
		for(int i=1; i>0; i++)
		{
			System.out.println("Hello World");
		}
	}
}

This program will print “Hello World” infinitely since the condition “i>0” will always be true.

This is a rather an unintentional and tedious way of doing this. You would probably never want to do things like printing “Hello world” an infinite number of times. This would probably be a programming error. But using infinite loops can also be intentional according to the requirements of a program. An elegant way of writing infinite loops are given below.

Using For

for(;;)
{
	// statements or expressions to be executed.
}

Using While

while(true) 
{
	// statements or expressions to be executed.

}

Using Do While

do {
	// statements or expressions to be executed.

} while (true);

In the above code, the statements or expressions will be executed infinitely and there will be no confusion too.

But, one important thing has to be taken into consideration while writing infinite Loops.

An infinite loop must contain a break statement. An infinite loop must have an exit condition that has to be executed once the goal of the program has been met. For example, you may want to write a program in which the computer guesses a number from 1 to 10 and the user also is asked to guess a number from 1 to 10, and the program only exits when the user’s guess matches that of the computer’s.

import java.util.Scanner; 
public class RandomNumber {
	public static void main(String a[]) {       
		while (true) {
			System.out.println("Computer is guessing a number\n");
			int computersNumber = (int) (Math.random()*10);		
			System.out.println(" ...... Done\n");
			System.out.println("Computer has guessed a number. It's your turn. Enter a number between 1 and 10\n");
			Scanner input = new Scanner(System.in);
			int usersNumber = input.nextInt();
			if(usersNumber == computersNumber) {
				System.out.println("Congrats! You've guessed the correct number. You can get out of the loop\n");
				break;
			}
			else {
				System.out.println("Oops! Sorry. Your guess did not match. Please try again.\n");
			}
		}
	}
}

We usually use:

while(true) {

}

Since it is more readable and clear way of generating code as it clarifies to the reader that the code has been intended to be an infinite loop. Also, the break condition is very necessary when we want to come out and should be thought and implemented as per the program requirements.