Overview of JAVA

Java is a two things:

One is Programming language

and another one is platform

Java Programming language

Java is a high-level programming language that is all of the following:

Simple

Object-oriented

Distributed

Interpreted

Robust

Secure

Architecture-neutral

Portable

High-performance

Multithreaded

Dynamic

Java is also unusual in that each Java program is both compiled and interpreted. With a compiler, you translate a Java program into an intermediate language called java bytecodes – the platform-independent codes interpreted by the Java interpreter. With an interpreter, each java bytecode instruction is parsed and run on the computer.

Compilation happens just once; interpretation occurs each time the program is executed.

The following figure illustrates how this works

How a Java Program works

You can think of Java bytecodes as the machine code instructions for the java Virtual Machine (JVM). Every Java interpreter, whether it’s a Java development tool or a Web browser that can run java applets, is an implementation of the Java VM. The Java VM can also be implemented in hardware.

Java bytecodes help make “write once, run anywhere” possible. You can compile your Java program into bytecodes on any platform that has a Java compiler. The bytecodes can then be run on any implementation of the Java VM. For example, the same Java program can run on Windows NT, Solaris, and Macintosh.