JAVA : Programming Language

How Java Got Evolved?
1. Fundamental reasons for computer language development:

• To adapt to changing environments & uses
• To implement refinements& improvements in art of programming

2. Era before Java

• Programming through toggling of switches on front panel
• Assembly Language
• FORTRAN
• C (Structured Programming)
• C++ (Object-Orientation for complexity management)

3. Java is no exception

• Java = C++ - {Problem Areas}
• Also, Java = C (Syntax) + C++ (Object-Orientation)

Scenarios that led to creation of Java

• Variety of CPU were existing in late 80’s & embedded systems were gaining popularity
• Developing compiler for each of them was expensive & time-consuming
• So, a platform independent solution was needed
• Internet also started spreading at that time

-Portability: Low-Priority Problem --> High Profile Necessity

• In 1991, James Gosling at Sun Microsystems conceived Oak as an architecturally neutral solution for portability
• Later, Oak was renamed to Java in 1995

Why Java is important to Internet?

• Internet = Static Information + Dynamic Part
• Dynamic part requires (unknown) programs from elsewhere to run on your computer

- Issues of Portability & Security

• As a solution, Java provided Applets which are portable and secure
• Applets are tiny Java programs which are:

- Transmitted over Internet
- Executed by Java-compatible Web Browser
- Can react to user-inputs and change dynamically

Protability & Security: Who is behind the scene?

• Java’s Magic: Bytecode

- Bytecode is highly optimized set of instructions designed to be executed by Java 
run-time system, which is called Java Virtual Machine (JVM)

• JVM is essentially an interpreter
• Portability: Just provide JVM for desired platform
• Security: JVM controls bytecode execution and prevents Applets from accessing different parts of computers and applications to generate side-effects

Features of Java

• Portable
• Secure
• Simple

- Easy to learn & use effectively
- Small number of clear ways of doing a task

• Object-Oriented

- Purely O-O

• Robustness

- Reliable execution of code on multiple platforms
- Through: strictly-typed, auto de-allocation, exception-handling

• Multithreaded

- Provides constructs for multithreading and auto multiprocess synchronization

• Architecture-Neutral

- Write-one; run anywhere, anytime; forever

• Interpreted and High Performance

- Through bytecode which is an engineered solution for interpretation

• Distributed

- Supports TCP/IP as designed for Internet
- RMI: Unparallel level of abstraction to client-server programming

• Dynamic

- Uses run-time type information to verify and resolve access to objects at run-time
-->Allows dynamic linking of code in safe & expedient environment manner Robustness


Myths About Java

• Java is Internet version of C++
• Java will replace C++
• Java programming is simple
• Java increases productivity
• All software should be coded in Java

Continuing Revolution

• Java Standard Editions (J2SE)

- 1.7 (early development)
- 1.6 (stable, current)
- 1.5 (stable)
- 1.4 (stable)
- 1.3 (obsolete)
- 1.2 (no longer actively supported)

• Java Enterprise Editions:

- J2EE 1.4
- Java EE 5

• Java for Micro Devices

- J2ME

References
Books:

• Java 2 Complete Reference, 5th Ed., by Herbert Schildt
• J2EE Unleashed by Paul Allen, SAMS Publisher
• CodeNotes for J2EE by Gregory Brill

Websites:
www.javapassion.com
www.java.sun.com