if « Statements « SCJP

5.7.1.The basic format of an if statement
5.7.2.The expression in an if statement must be a boolean expression.
5.7.3.Use an else block to execute code that is executed under the conditions that the test returns false.
5.7.4.Use if/else in a nested fashion, refining conditions to more specific, or narrower, tests at each point.