The Java® Language Specification, Java SE 7 Edition, Fourth Edition

14.9. The if Statement

The if statement allows conditional execution of a statement or a conditional choice of two statements, executing one or the other but not both.

IfThenStatement:    if ( Expression ) StatementIfThenElseStatement:    if ( Expression ) StatementNoShortIf else StatementIfThenElseStatementNoShortIf:    if ( Expression ) StatementNoShortIf else StatementNoShortIf

The Expression must have type boolean or Boolean, or a compile-time error occurs.

14.9.1. The if-then Statement

An if-then statement is executed by first evaluating the Expression. If the result is of type Boolean, it is subject to unboxing conversion (§5.1.8).

If evaluation of the Expression or the subsequent unboxing conversion (if any) completes abruptly for some ...