EXPRESSIONS

Runtime Evaluation of Method Invocation

15.11.4

For the method

m

:

If

m

is

public

, then

m

 is accessible. (All members of interfaces are

public

( 9.2)).

If

m

 is

protected

, then

m

 is accessible if and only if either

T

 is in the same

package as

C

, or

C

 is

T

 or a subclass of

T

.

If

m

 has default (package) access, then

m

 is accessible if and only if

T

 is in the

same package as

C

.

If

m

 is

private

, then

m

 is accessible if and only if and

C

 is

T

.

If either

T

 or

m

is not accessible, then an

IllegalAccessError

 occurs ( 12.3).

15.11.4.4

Locate Method to Invoke

The strategy for method lookup depends on the invocation mode.

If the invocation mode is

static

, no target reference is needed and overriding

is not allowed. Method

m

 of class

T

 is the one to be invoked.

Otherwise, an instance method is to be invoked and there is a target reference.

If the target reference is

null

, a

NullPointerException

 is thrown at this point.

Otherwise, the target reference is said to refer to a

target object

 and will be used as

the value of the keyword

this

 in the invoked method. The other four possibilities

for the invocation mode are then considered.

If the invocation mode is

nonvirtual

, overriding is not allowed. Method

m

 of

class

T

 is the one to be invoked.

Otherwise, the invocation mode is

interface

,

virtual

, or

super

, and over 

riding may occur. A

dynamic method lookup

is used. The dynamic lookup process

starts from a class

S

, determined as follows:

If the invocation mode is

interface

 or

virtual

, then

S

is initially the actual

run time class

R

 of the target object. If the target object is an array,

R

 is the

class

Object

. (Note that for invocation mode

interface

,

R

 necessarily

implements

T

; for invocation mode

virtual

,

R

 is necessarily either

T

 or a

subclass of

T

.)

If the invocation mode is

super

, then

S

 is initially the superclass of the class

C

 that contains the method invocation.

The dynamic method lookup uses the following procedure to search class

S

, and

then the superclasses of class

S

, as necessary, for method

m

.

1. If class

S

 contains a declaration for a method named

m

 with the same descriptor

(same number of parameters, the same parameter types, and the same return

type) required by the method invocation as determined at compile time

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