Java 2 Platform, Standard Edition

Java 2 Platform, Standard Edition or J2SE is a collection of java Application Programming Interfaces targeting Java platform applications running on a workstation.

Table of contents 1 General APIs 1.1 java.io 1.2 java.lang 1.2.1 java.lang.ref 1.2.2 java.lang.reflection 1.3 java.math 1.4 java.net 1.5 java.text 1.6 java.util 2 More specialized APIs 2.1 java.applet 2.2 java.beans 2.3 java.awt 2.4 java.rmi 2.5 java.security 2.6 java.sql 2.7 javax.swing 3 Additional Information

General APIs

java.io

Routines for normal input and output. This includes streams and filehandling.

java.lang

Contains classes thought applicable to most java programs. This package contains standard java types like Integers and Strings as well as basic exceptions, math functions, threading, security functions, as well as some information on the underlying native system.

Classes in java.lang package are always available to the programmer, without needing a special import declaration at the beginning of a sourcecode file.

java.lang.ref

Special routines for interacting with the garbage collector. For example, one can create a weak reference, which allows one to refer to an object, without preventing the garbage collector from cleaning it up. This is useful in caches, where if nothing else refers to an object held by the cache, the garbage collector may clean it up at whim.

java.lang.reflection

Routines for using the Reflection API. The main use of Reflection is to call classes and methods just by knowing their names. This supports very dynamic programming, at the cost of not having safe compile-time checks to see if the class actually exists.

java.math

Numerical routines.

java.net

Special IO routines for networks. This includes the ability to easily request files over HTTP, as well as other common transactions.

java.text

Parsing routines for strings. Support for different human-readable languages and locale-specific parsing is also included.

java.util

Routines for useful data structures. These data structures aggregate objects, with varying useful properties. Also includes the Collections API, which is a very organized way to handle data structures, influenced heavily by the Design Patterns community.

More specialized APIs

java.applet

Routines to create applets. Applets allow applications to be downloaded over a network and run within a guarded sandbox. Security restrictions may be applied to applets, so they are not allowed to execute potentially hostile code from within the sandbox. A developer may apply a digital signature to an applet to label it as "safe," removing most of the restrictions, but this typically requires the developer to pay hundreds of US dollars a year to a certificate issuing agency such as Thawte or Entrust.

java.beans

Routines to call code dynamically, using the Reflection API.

java.awt

The Abstract Windowing Toolkit contains routines to support basic GUI operations. These GUIs use basic windows from the underlying native system. Many independent implementations of the Java API (such as the GNU project's libgcj[?]) implement everything but AWT, as AWT is not at all necessary for most server-side applications of Java technology.

java.rmi

Support for remote communication between two java applications.

java.security

Support for security. Includes message digest algorithm.

java.sql

The JDBC API for accessing SQL databases.

javax.swing

Swing is a collection of routines that build upon java.awt. It uses 2D drawing routines to exercise greater control over new windows than the underlying native platform normally allows. One cost of this flexibility is that Swing elements may not exist outside of java.awt windows.

Swing is a very rich system in its own right. There is support for "look and feels," so that widgets in the GUI can imitate those from the underlying native system (except when IP rights force workarounds, as noted in the Legal Issues section), or a completely fictional one. Also, design patterns permeate the system, especially a modified model-view-controller[?] pattern, so programming is done cleanly, with good separation of function from appearance. However, one inconsistency is that (as of JDK 1.3) fonts are drawn by the underlying native system, and not by Java. This makes it difficult to have utter, complete control of text size, though workarounds exist such as drawing fonts as application-supplied bitmaps. In general, layouts should be used, which keep elements within a GUI aesthetically consistent despite minor variations between platforms.

Additional Information

• The complete java documentation for the API can be found out http://java.sun.com/j2se/1.4/docs/api/index .
• See also http://java.sun.com/j2se/1.4/index