Читать книгу OCP Oracle Certified Professional Java SE 17 Developer Study Guide - Jeanne Boyarsky - Страница 172

Often, we want to execute a block only under certain circumstances. The if statement, as shown in Figure 3.1, accomplishes this by allowing our application to execute a particular block of code if and only if a boolean expression evaluates to true at runtime.

FIGURE 3.1 The structure of an if statement

For example, imagine we had a function that used the hour of day, an integer value from 0 to 23, to display a message to the user:

if(hourOfDay < 11) System.out.println("Good Morning");

If the hour of the day is less than 11, then the message will be displayed. Now let's say we also wanted to increment some value, morningGreetingCount, every time the greeting is printed. We could write the if statement twice, but luckily Java offers us a more natural approach using a block:

if(hourOfDay < 11) { System.out.println("Good Morning"); morningGreetingCount++; }