Java

About Java

Java technology is both a programming language and a platform independent.Java offers a much more reliable and predictable scheduling mechanism, memory handling methods, different memory models, a more predictable threading and synchronization model, asynchronous event handling, and high-resolution time handling. It makes predictable execution the first priority in all trade-off decisions, sometimes at the expense of typical general-purpose computing performance measures.



There are two principal products in the Java Platform, Standard Edition (Java SE, formerly known as J2SE) family:

1.Java SE Runtime Environment(JRE)

2.Java SE Development Kit (JDK).

The JRE provides the Java APIs, Java virtual machine, and other components necessary to run applets and applications written in the Java programming language. It is also the foundation for the technologies in the Java Platform, Enterprise Edition (Java EE) for enterprise software development and deployment. The JRE does not contain tools and utilities such as compilers or debuggers for developing applets and applications.

The Java Programming Language

In the Java programming language, all source code is first written in plain text files ending with the .java extension. Those source files are then compiled into .class files by the Java compiler (javac). A .class file does not contain code that is native to your processor; it instead contains bytecodes-- the machine language of the Java Virtual Machine. The Java launcher tool (java) then runs your application with an instance of the Java Virtual Machine.

The Java Platform

A platform is the hardware or software environment in which a program runs.The Java platform has two components:

1.The Java Virtual Machine (JVM)

2.The Java Application Programming Interface (API)

The API is a large collection of ready-made software components that provide many useful capabilities, such as graphical user interface (GUI) widgets. It is grouped into libraries of related classes and interfaces; these libraries are known as packages.JVM is a stack machine,this makes it simple to generate JVM code, and makes the JVM code compact.The JVM converts the class files into the bytecodes.