14.1

Normal and Abrupt Completion of Statements

BLOCKS AND STATEMENTS

14.1   Normal and Abrupt Completion of Statements

Poirot's abrupt departure had intrigued us all greatly.

 Agatha Christie,

The Mysterious Affair at Styles

 (1920), Chapter 12

Every statement has a normal mode of execution in which certain computational

steps are carried out. The following sections describe the normal mode of execu 

tion for each kind of statement. If all the steps are carried out as described, with no

indication of abrupt completion, the statement is said to

complete normally

. How 

ever, certain events may prevent a statement from completing normally:

The

break

 ( 14.13),

continue

 ( 14.14), and

return

 ( 14.15) statements

cause a transfer of control that may prevent normal completion of statements

that contain them.

Evaluation of certain Java expressions may throw exceptions from the Java

Virtual Machine; these expressions are summarized in  15.5. An explicit

throw

 ( 14.16) statement also results in an exception. An exception causes a

transfer of control that may prevent normal completion of statements.

If such an event occurs, then execution of one or more statements may be ter 

minated before all steps of their normal mode of execution have completed; such

statements are said to

complete abruptly

. An abrupt completion always has an

associated

reason

, which is one of the following:

A

break

 with no label

A

break

 with a given label

A

continue

 with no label

A

continue

 with a given label

A

return

 with no value

A

return

 with a given value

A

throw

 with a given value, including exceptions thrown by the Java Virtual

Machine

The terms  complete normally  and  complete abruptly  also apply to the

evaluation of expressions ( 15.5). The only reason an expression can complete

abruptly is that an exception is thrown, because of either a

throw

 with a given

value ( 14.16) or a run time exception or error ( 11,  15.5).

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