14.7

Expression Statements

BLOCKS AND STATEMENTS

identifier as a local variable or as the parameter of an exception handler ( 14.18)

does not hide a statement label with the same name.

A labeled statement is executed by executing the immediately contained

Statement

. If the statement is labeled by an

Identifier

 and the contained

Statement

completes abruptly because of a

break

 with the same

Identifier

, then the labeled

statement completes normally. In all other cases of abrupt completion of the

Statement

, the labeled statement completes abruptly for the same reason.

14.7   Expression Statements

Certain kinds of expressions may be used as statements by following them with

semicolons:

ExpressionStatement:

StatementExpression

 ;

StatementExpression:

Assignment

PreIncrementExpression

PreDecrementExpression

PostIncrementExpression

PostDecrementExpression

MethodInvocation

ClassInstanceCreationExpression

An

expression statement

 is executed by evaluating the expression; if the

expression has a value, the value is discarded. Execution of the expression state 

ment completes normally if and only if evaluation of the expression completes

normally.

Unlike C and C++, the Java language allows only certain forms of expressions

to be used as expression statements. Note that Java does not allow a  cast to

void

void

 is not a type in Java so the traditional C trick of writing an expres 

sion statement such as:

(void) ... ;

//

This idiom belongs to C, not to Java!

does not work in Java. On the other hand, Java allows all the most useful kinds of

expressions in expressions statements, and Java does not require a method invoca 

tion used as an expression statement to invoke a

void

 method, so such a trick is

almost never needed. If a trick is needed, either an assignment statement ( 15.25)

or a local variable declaration statement ( 14.3) can be used instead.

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