Blocks and Statements - The Java Language Specification - page 376

is almost never needed. If a trick is needed, either an assignment statement (§ 15.26 )
or a local variable declaration statement (§ 14.4 ) can be used instead.
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 ) Statement
IfThenElseStatement:
if ( Expression ) StatementNoShortIf else Statement
IfThenElseStatementNoShortIf:
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 reason, the if-then statement completes abruptly for the same reason.
Otherwise, execution continues by making a choice based on the resulting value:
• If the value is true , then the contained Statement is executed; the if-then statement
completes normally if and only if execution of the Statement completes normally.
• If the value is false , no further action is taken and the if-then statement completes
normally.
14.9.2. The if-then-else Statement
An if-then-else 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 reason, then the if-then-else statement completes abruptly for the same
reason.
Otherwise, execution continues by making a choice based on the resulting value: