Читать книгу OCP Oracle Certified Professional Java SE 17 Developer Study Guide - Jeanne Boyarsky - Страница 197

The single most important thing you should be aware of when you are using any repetition control structures is to make sure they always terminate! Failure to terminate a loop can lead to numerous problems in practice, including overflow exceptions, memory leaks, slow performance, and even bad data. Let's take a look at an example:

int pen = 2; int pigs = 5; while(pen < 10) pigs++;

You may notice one glaring problem with this statement: it will never end. The variable pen is never modified, so the expression (pen < 10) will always evaluate to true. The result is that the loop will never end, creating what is commonly referred to as an infinite loop. An infinite loop is a loop whose termination condition is never reached during runtime.

Anytime you write a loop, you should examine it to determine whether the termination condition is always eventually met under some condition. For example, a loop in which no variables are changing between two executions suggests that the termination condition may not be met. The loop variables should always be moving in a particular direction.

In other words, make sure the loop condition, or the variables the condition is dependent on, are changing between executions. Then, ensure that the termination condition will be eventually reached in all circumstances. As you learn in the last section of this chapter, a loop may also exit under other conditions, such as a break statement.