The Java Platform

Java Platform

Ø A platform is a combination of hardware and software which creates an environment for the execution of an application.

Ø The Java platform provides an environment for developing applications that can be executed on various hardware and OS.

Ø Java platform is a software-only platform that runs on top of other hardware-based platforms. It contains the Java Runtime Environment (JRE) with components namely, Java Virtual Machine (JVM) and Java class library

Java Platform Editions

Java Standard Edition

Ø The Java Standard Edition (Java SE) is for building desktop applications and applets. These applications typically serve only a small number of users at one time.

Java Enterprise Edition

Ø The Java Enterprise Edition (Java EE) is tailored for more complex applications to suit medium to large businesses. Typically they will be server based applications focusing on serving the needs of lots users at one time.

Ø Note: The Java EE contains many of the Java APIs found in the Java SE.

Java Micro Edition

Ø The Java Micro Edition is for applications used on mobile (e.g., cell phone, PDA) and embedded devices (e.g., TV tuner box, printers).

Editions of Java

Ø Java Standard Edition (Java SE) - Java SE is a base platform for other editions. Developers use the Java SE platform to develop console and networking applications for desktop computers.

Ø Java Enterprise Edition (Java EE) - Java EE is built on top of Java SE platform. The Java EE platform provides a standard specification for developing and deploying distributed, scalable, and multi-tier enterprise applications. The enterprise applications are large server-side business applications with complex business logics.

Ø Java Mobile Edition (Java ME) - Java ME is a robust platform for developing embedded Java applications for consumer electronic devices, such as mobiles, Personal Digital Assistants (PDAs), TV set-top boxes, and so on.

JDK Parts

Ø One part contains the utilities like javac, debugger, jar which helps in compiling the source code (.java files) into byte code (.class files) and debug the programs.

Ø The other part is the JRE, which contains the utilities like java which help in running/executing the byte code. If we want to write programs and run them, then we need the JDK installed.

Parts of JRE

Ø JRE contains the JVM, the java classes/packages and the run-time libraries. If we do not want to write programs, but only execute the programs written by others, then JRE alone will be sufficient.

Evolution of Java SE

Ø JDK 1.0 Creation of packages with classes in the standard library

Ø JDK 1.1 Included an event delegation model for Graphical User Interface (GUI) package AWT, JavaBeans, and Java Database Connectivity (JDBC) API

Ø JDK 1.2 (Java 2) Included a new graphical API, named Swing. Also added APIs for reflection and collection framework (based on data structure)

Ø JDK 1.3 Included a directory interface to lookup for components, named, Java Naming and Directory Interface (JNDI)

Ø JDK 1.4 Included regular expression API, assertions, exception chaining, channel-based I/O API, an XML API for parsing and processing .

Ø Java SE 7

Ø Java SE 7 is the new major release of Java with internal version number as 1.7. The significant changes of Java SE 7 have been made at the language and API level.

Downloading and Installing JDK

Ø To develop Java applications, you need JDK installed on the system. Since, Oracle has acquired Sun Microsystems; the different versions of JDK are available for installation at Oracle’s site.

Ø To download and install jdk goto www.oracle.com

Directory Structure of JDK

Directory	Description
Bin	Contains tools that are used for developing a java application.
Db	Contains a relational database named Apache Derby
Include	Contains header files that are used to interact with C applications
Jre	Represents the JRE used by the JDK