Chapter 4. The Java Platform
Chapter 2, "Java Syntax
from the Ground Up", and Chapter 3, "Object-Oriented Programming in Java",
documented the Java programming language. This chapter switches
gears and covers
the Java platform, which is the vast collection of
predefined classes available to every Java program, regardless of
the underlying host system on which it is running. The
classes of the Java platform are collected into related groups, known
as packages. This chapter begins with an overview of the
packages of the Java platform that are documented in this book. It then moves on to demonstrate, in
the form of short examples, the most useful classes in these packages.
4.1. Java Platform Overview
Table 4-1 summarizes the key packages of
the Java platform that are covered in this book.
Table 4-1. Key Packages of the Java Platform
The JavaBeans component model for reusable,
embeddable software components.
classes that define bean context objects that
hold and provide services to the JavaBeans objects they
Classes and interfaces for input and output. Although
some of the classes in this package are for working
directly with files, most are for working with streams
of bytes or characters.
The core classes of the language, such as
Classes that define weak references to objects. A
weak reference is one that does not prevent the
referent object from being garbage-collected.
Classes and interfaces that allow Java programs to
reflect on themselves by examining the constructors,
methods, and fields of classes.
A small package that contains classes for
arbitrary-precision integer and floating-point
Classes and interfaces for networking with other
Classes and interfaces for access control and
authentication. Supports cryptographic message digests
and digital signatures.
A package that supports access control lists. Deprecated
and unused as of Java 1.2.
Classes and interfaces for working with public key
used with DSA and RSA public-key encryption.
Classes and interfaces for transparent
keys and parameters used in public-key cryptography.
Classes and interfaces for working with text in
Various utility classes, including the powerful
collections framework for working with collections of
Classes for reading and writing JAR files.
Classes for reading and writing ZIP files.
Classes and interfaces for
encryption and decryption of
Interfaces that represent the Diffie-Hellman
public/private keys used in the Diffie-Hellman key
Classes that define transparent representations of
keys and parameters used in cryptography.
Table 4-1 does not list all the
packages in the Java platform, only those documented in this book. Java also defines numerous packages for graphics and graphical
user interface programming and for distributed, or enterprise,
computing. The graphics and GUI packages are
java.awt and javax.swing
and their many subpackages. These packages, along with the
java.applet package, are documented in
Java Foundation Classes in a Nutshell
enterprise packages of Java include
org.omg.CosNaming, and all of their
subpackages. These packages, as well as several standard
extensions to the Java platform, are documented in the book
Java Enterprise in a Nutshell (O'Reilly).
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