EXECUTION

Virtual Machine Exit

12.9

12.7   Finalization of Classes

If a class declares a class method

classFinalize

 that takes no arguments and

returns no result:

static void classFinalize() throws Throwable {

. . .

 }

then this method will be invoked before the class is unloaded ( 12.8). Like the

finalize

 method for objects, this method will be automatically invoked only

once. This method may optionally be declared

private

,

protected

, or

public

.

12.8   Unloading of Classes and Interfaces

A Java Virtual Machine may provide mechanisms whereby classes are

unloaded

.

The details of such mechanisms are not specified in this version of the Java Lan 

guage Specification. In general, groups of related class and interface types will be

unloaded together. This can be used, for example, to unload a group of related

types that have been loaded using a particular class loader. Such a group might

consist of all the classes implementing a single applet in a Java based browser

such as HotJava, for example.

A class may not be unloaded while any instance of it is still reachable ( 12.6).

A class or interface may not be unloaded while the

Class

 object that represents it

is still reachable.

Classes that declare class finalizers ( 12.7) will have these finalizers run

before they are unloaded.

12.9   Virtual Machine Exit

A Java Virtual Machine terminates all its activity and

exits

 when one of two things

happens:

All the threads that are not daemon threads ( 20.20.24) terminate.

Some thread invokes the

exit

 method ( 20.16.2) of class

Runtime

 or class

System

 and the exit operation is not forbidden by the security manager

( 20.17.13).

A Java program can specify that the finalizers of all objects that have finalizers,

and all classes that have class finalizers, that have not yet been automatically

invoked are to be run before the virtual machine exits. This is done by invoking

the method

runFinalizersOnExit

 of class

System

 with the argument

true

. The

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