BLOCKS AND STATEMENTS

The

throw

 Statement

14.16

A

return

 statement with an

Expression

 attempts to transfer control to the

invoker of the method that contains it; the value of the

Expression

 becomes the

value of the method invocation. More precisely, execution of such a

return

 state 

ment first evaluates the

Expression

. If the evaluation of the

Expression

 completes

abruptly for some reason, then the

return

 statement completes abruptly for that

reason. If evaluation of the

Expression

 completes normally, producing a value

V

,

then the

return

 statement completes abruptly, the reason being a

return

 with

value

V

.

It can be seen, then, that a

return

 statement always completes abruptly.

The preceding descriptions say  attempts to transfer control  rather than just

 transfers control  because if there are any

try

 statements ( 14.18) within the

method or constructor whose

try

 blocks contain the

return

 statement, then any

finally

 clauses of those

try

 statements will be executed, in order, innermost to

outermost, before control is transferred to the invoker of the method or construc 

tor. Abrupt completion of a

finally

 clause can disrupt the transfer of control ini 

tiated by a

return

 statement.

14.16   The

throw

 Statement

A

throw

 statement causes an exception ( 11) to be thrown. The result is an imme 

diate transfer of control ( 11.3) that may exit multiple statements and multiple

constructor, static and field initializer evaluations, and method invocations until a

try

 statement ( 14.18) is found that catches the thrown value. If no such

try

statement is found, then execution of the thread ( 17,  20.20) that executed the

throw

 is terminated ( 11.3) after invocation of the

UncaughtException

 method

( 20.21.31) for the thread group to which the thread belongs.

ThrowStatement:

throw

Expression

 ;

The

Expression

 in a throw statement must denote a variable or value of a ref 

erence type which is assignable ( 5.2) to the type

Throwable

, or a compile time

error occurs. Moreover, at least one of the following three conditions must be true,

or a compile time error occurs:

The exception is not a checked exception ( 11.2) specifically, one of the fol 

lowing situations is true:

N

The type of the

Expression

 is the class

RuntimeException

 or a subclass of

RuntimeException

.

N

The type of the

Expression

 is the class

Error

 or a subclass of

Error

.

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