8.4.5

Method Body

CLASSES

A method that overrides or hides another method ( 8.4.6), including methods

that implement

abstract

 methods defined in interfaces, may not be declared to

throw more checked exceptions than the overridden or hidden method.

More precisely, suppose that

B

 is a class or interface, and

A

 is a superclass or

superinterface of

B

, and a method declaration

n

 in

B

 overrides or hides a method

declaration

m

 in

A

. If

n

 has a

throws

 clause that mentions any checked exception

types, then

m

 must have a

throws

 clause, and for every checked exception type

listed in the

throws

 clause of

n

, that same exception class or one of its super 

classes must occur in the

throws

 clause of

m

; otherwise, a compile time error

occurs.

See  11 for more information about exceptions and a large example.

8.4.5   Method Body

A

method body

 is either a block of code that implements the method or simply a

semicolon, indicating the lack of an implementation. The body of a method must

be a semicolon if and only if the method is either

abstract

 ( 8.4.3.1) or

native

( 8.4.3.4).

MethodBody:

Block

;

A compile time error occurs if a method declaration is either

abstract

 or

native

 and has a block for its body. A compile time error occurs if a method dec 

laration is neither

abstract

 nor

native

 and has a semicolon for its body.

If an implementation is to be provided for a method but the implementation

requires no executable code, the method body should be written as a block that

contains no statements:  

{ }

 .

If a method is declared

void

, then its body must not contain any

return

statement ( 14.15) that has an

Expression

.

If a method is declared to have a return type, then every

return

 statement

( 14.15) in its body must have an

Expression

. A compile time error occurs if the

body of the method can complete normally ( 14.1). In other words, a method with

a return type must return only by using a return statement that provides a value

return; it is not allowed to  drop off the end of its body. 

Note that it is possible for a method to have a declared return type and yet

contain no return statements. Here is one example:

164