Java Infinite Loops


An infinte loop is a loop statement (for, while, do-while) which does not end on its own.

The test condition of a looping statement decides whether the loop body will execute or not. So a test condition which is always true will keep on executing the body of the loop, forever. That’s the case in an infinte loop.

Example

// Infinite For Loop for ( ; ; ) { // some code here } // Infinite While Loop while (true) { // some code here } // Infinite Do While Loop do { // some code here } while (true);

Normally, if your loop is running infinitely, it is an error that should not occur as an infinite loop does not stop and prevents the rest of the program from running.

for(int i=0;i<100;i++){ if(i==49){ i=0; } }

The loop above runs infinitely because every time i approaches 49, it is set to be 0.This is to say that i never reaches 100 to terminate the loop, so the loop is an infinite loop.

But a program stuck in such a loop will keep using computer resources indefinitely. This is undesirable, and is a type of ‘run-time error’.

Infinite Loop by opposite iteration

Another example of an Infinite Loop can be seen below:

for(int i=0;i<=10;i--) System.out.println(i);

In the above example, the initial value of i is 0. Since value of i is less than equal to 10, we decrement the value of i by 1, so i will now be -1. Hence, the loop will be infinite.

Similarly, an example of an infinite while loop example can be seen below:

int i=1; while(i>=1) { System.out.println(i); i+=1; }

Here, i will always be greater than 1, so the program will be in an infinite loop.

To prevent the error, programmers use a break statement to break out of the loop. The break executes only under a particular condition. Use of a selection statement like if-else ensures the same.

while (true) { // do something if(conditionToEndLoop == true) break; // do more }

The main advantage of using an infinite loop over a regular loop is readability.

Sometimes, the body of a loop is easier to understand if the loop ends in the middle, and not at the end/beginning. In such a situation, an infinite loop will be a better choice.

Uses

A lot of programs (embedded control software, graphical applications, games, web & DBMS servers, and even Unix or Posix or Linux kernels) is organized around an infinite event loop. Servers also listen to incoming traffic in an endless loop.

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