Introduction To Java

[ProJecT]

Java:

Java is a programming language originally developed by Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM) regardless of computer architecture.

 

Philosophy

 

Primary goals

 

There were five primary goals in the creation of the Java language:

 

  1. It should be "simple, object oriented, and familiar".

  2. It should be "robust and secure".

  3. It should be "architecture neutral and portable".

  4. It should execute with "high performance".

  5. It should be "interpreted, threaded, and dynamic".

 

Syntax

 

 

The syntax of Java is largely derived from C++. Unlike C++, which combines the syntax for structured, generic, and object-oriented programming, Java was built almost exclusively as an object oriented language. All code is written inside a class and everything is an object, with the exception of the intrinsic data types (ordinal and real numbers, boolean values, and characters), which are not classes for performance reasons.

 

Java suppresses several features (such as operator overloading and multiple inheritance) for classes in order to simplify the language and to prevent possible errors and anti-pattern design.

 

Class libraries

 

    * Java libraries are the compiled byte codes of source code developed by the JRE implementor to support application development in Java. Examples of these libraries are:

          o The core libraries, which include:

                + Collection libraries that implement data structures such as lists, dictionaries, trees and sets

                + XML Processing (Parsing, Transforming, Validating) libraries

                + Security

                + Internationalization and localization libraries

          o The integration libraries, which allow the application writer to communicate with external systems. These libraries include:

                + The Java Database Connectivity (JDBC) API for database access

                + Java Naming and Directory Interface (JNDI) for lookup and discovery

                + RMI and CORBA for distributed application development

          o User Interface libraries, which include:

                + The (heavyweight, or native) Abstract Windowing Toolkit (AWT), which provides GUI components, the means for laying out those components and the means for handling events from those components

                + The (lightweight) Swing libraries, which are built on AWT but provide (non-native) implementations of the AWT widgetry

                + APIs for audio capture, processing, and playback

    * A platform dependent implementation of Java virtual machine (JVM) that is the means by which the byte codes of the Java libraries and third party applications are executed

    * Plugins, which enable applets to be run in Web browsers

    * Java Web Start, which allows Java applications to be efficiently distributed to end users across the Internet

    * Licensing and documentation.

 

Editions

Sun has defined and supports four editions of Java targeting different application environments and segmented many of its APIs so that they belong to one of the platforms. The platforms are:

 

    * Java Card for smartcards

    * Java Platform, Micro Edition (Java ME) — targeting environments with limited resources,

    * Java Platform, Standard Edition (Java SE) — targeting workstation environments, and

    * Java Platform, Enterprise Edition (Java EE) — targeting large distributed enterprise or Internet environments.

 

The classes in the Java APIs are organized into separate groups called packages. Each package contains a set of related interfaces, classes and exceptions. Refer to the separate platforms for a description of the packages available.