Java-In-a-Nutshell

Motivation

• Need for a platform independent language to embed in various consumer systems.
• WWW ( World Wide Web) originated at the same time boosted java development further.

Java Applets

• An applet is a special program transmitted over the internet which is automatically executed by a JAVA compatible browser.
• Dynamic, self-executing program.
• Carries out basic functions like displaying data, handling user data , simple functions etc.

Bytecode

• JAVA compiler generates bytecode ( highly optimised intermediate code).
• It can be executed by JVMs of various kinda of systems.
• Achieves Portability : bytecode geberated on one system can be executed in any other system ( JVM is implemented differently for differnt systems.)

JVM

• A java runtime environment which contains the entire java program and prevents any side effects outside it.
• Contains JIT(Just in time) compiler which compiles selected portions of bytecode to native code in real time by performing various run-time checks.

Servlet

• A small program that executed on server to provide some basic functionality. ( similar to applets on clients)
• Used to create dynamic content at the server side, which is then sent to the client side.

Buzzwords

• Simple : Easy to learn and use
• Object-Oriented : treats everything as an object in the object model.
• Robust : written programs execute in a predictable manner ; reliable ; free from common errors ; strictly typed language
• Architecture-Neutral : programs execute independent of underlying architecture.
• Multithreaded : programs can do multiple things simultaneously.
• Interpreted and high performance : unlike most interpreted languages , java achieves high performance even though it uses bytecode.