EXPRESSIONS

Runtime Evaluation of Method Invocation

15.11.4

15.11.4.6

Implementation Note: Combining Frames

In order to allow certain kinds of code optimization, implementations are permit 

ted some freedom to combine activation frames. Suppose that a method invocation

within class

C

 is to invoke a method

m

 within class

S

. Then the current activation

frame may be used to provide space for

S

 instead of creating a new activation

frame only if one of the following conditions is true:

Class

C

 and class

S

 have the same class loader ( 20.14) and class

S

 is not

SecurityManager

 or a subclass of

SecurityManager

.

Class

S

 has no class loader (this fact indicates that it is a system class); class

S

is not

SecurityManager

 or a subclass of

SecurityManager

; and method

m

is known not to call, directly or indirectly, any method of

SecurityManager

( 20.17) or any of its subclasses.

15.11.4.7

Example: Target Reference and Static Methods

When a target reference is computed and then discarded because the invocation

mode is

static

, the reference is not examined to see whether it is

null

:

class Test {

static void mountain() {

System.out.println("Monadnock");

}

static Test favorite(){

System.out.print("Mount ");

return null;

}

public static void main(String[] args) {

favorite().mountain();

}

}

which prints:

Mount Monadnock

Here

favorite

 returns

null

, yet no

NullPointerException

 is thrown.

15.11.4.8

Example: Evaluation Order

As part of an instance method invocation ( 15.11), there is an expression that

denotes the object to be invoked. This expression appears to be fully evaluated

before any part of any argument expression to the method invocation is evaluated.

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