BLOCKS AND STATEMENTS

Execution of

try catch

14.18.1

parameter

); the declared type of the exception parameter must be the class

Throwable

 or a subclass of

Throwable

, or a compile time error occurs. The

scope of the parameter variable is the

Block

 of the

catch

 clause. An exception

parameter must not have the same name as a local variable or parameter in whose

scope it is declared, or a compile time error occurs.

The scope of the name of an exception parameter is the

Block

 of the

catch

clause. The name of the parameter may not be redeclared as a local variable or

exception parameter within the

Block

 of the

catch

 clause; that is, hiding the name

of an exception parameter is not permitted.

Exception parameters cannot be referred to using qualified names ( 6.6), only

by simple names.

Exception handlers are considered in left to right order: the earliest possible

catch

 clause accepts the exception, receiving as its actual argument the thrown

exception object.

A

finally

 clause ensures that the

finally

 block is executed after the

try

block and any

catch

 block that might be executed, no matter how control leaves

the

try

 block or

catch

 block.

Handling of the

finally

 block is rather complex, so the two cases of a

try

statement with and without a

finally

 block are described separately.

14.18.1   Execution of

try catch

Our supreme task is the resumption of our onward, normal way.

 Warren G. Harding, Inaugural Address (1921)

A

try

 statement without a

finally

 block is executed by first executing the

try

block. Then there is a choice:

If execution of the

try

 block completes normally, then no further action is

taken and the

try

 statement completes normally.

If execution of the

try

 block completes abruptly because of a

throw

 of a

value

V

, then there is a choice:

N

If the run time type of

V

 is assignable ( 5.2) to the

Parameter

 of any

catch

clause of the

try

 statement, then the first (leftmost) such

catch

 clause is

selected. The value

V

 is assigned to the parameter of the selected

catch

clause, and the

Block

 of that

catch

 clause is executed. If that block com 

pletes normally, then the

try

 statement completes normally; if that block

completes abruptly for any reason, then the

try

 statement completes

abruptly for the same reason.

291