12

C H A P T E R

Execution

We must all hang together, or assuredly we shall all hang separately.

 Benjamin Franklin (July 4, 1776)

T

HIS chapter specifies activities that occur during execution of a Java program.

It is organized around the life cycle of a Java Virtual Machine and of the classes,

interfaces, and objects that form a Java program.

A Java Virtual Machine starts up by loading a specified class and then invok 

ing the method

main

 in this specified class. Section  12.1 outlines the loading,

linking, and initialization steps involved in executing

main

, as an introduction to

the concepts in this chapter. Further sections specify the details of loading ( 12.2),

linking ( 12.3), and initialization ( 12.4).

The chapter continues with a specification of the procedures for creation of

new class instances ( 12.5); finalization of class instances ( 12.6); and finaliza 

tion of classes ( 12.7). It concludes by describing the unloading of classes ( 12.8)

and the procedure followed when a virtual machine exits ( 12.9).

12.1   Virtual Machine Start Up

A Java Virtual Machine starts execution by invoking the method

main

 of some

specified class, passing it a single argument, which is an array of strings. In the

examples in this specification, this first class is typically called

Test

.

The manner in which the initial class is specified to the Java Virtual Machine

is beyond the scope of this specification, but it is typical, in host environments that

use command lines, for the fully qualified name of the class to be specified as a

command line argument and for following command line arguments to be used as

strings to be provided as the argument to the method

main

. For example, in a

UNIX implementation, the command line:

java Test reboot Bob Dot Enzo

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