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      JAVA is a distributed technology developed by James Gosling, Patric Naugton, etc., at Sun Micro System has released lot of rules for JAVA and those rules are implemented by JavaSoft Inc, USA (which is the software division of Sun Micro System) in the year 1990. The original name of JAVA is  OAK (which is a tree name). In the year 1995, OAK was revised and developed software  called JAVA (which is a coffee seed name).

JAVA released to the market in three categories J2SE (JAVA 2 Standard Edition), J2EE (JAVA 2 Enterprise Edition) and J2ME  (JAVA 2 Micro/Mobile Edition).

i. J2SE is basically used for developing client side applications/programs.

ii. J2EE is used for developing server side applications/programs.

iii.J2ME is used for developing server side applications/programs.

If you exchange the data between client and server programs (J2SE and J2EE), by default JAVA is having  on  internal  support  with  a  protocol  called  http.  J2ME  is  used  for  developing  mobile applications and  lower/system  level applications.  To  develop  J2ME  applications  we  must  use  a protocol called WAP (Wireless Applications Protocol).

FEATURES OF JAVA:

1)SIMPLE:
Java is a simple programming language,learning and practising java is eay because of its resemblence with C and C++.Also complex topics of C and C++ are eliminated in java.

2)OBJECT ORIENTED:
Unlike C++ Java is a purely object oriented programming  language.Java programs use objects and classes.

3)DITRIBUTED:
Information is distrbuted on various computers on a network.Using java we can write programs which capture information and distribute it to clients.

4)ROBUST:
Java programs will not crash easily because of its exception handling and its memory management features.

5)SECURE:
Java enables the construction of virus free and tamper free systems.

6)ARCHITECTURE NEUTRAL:
Java byte code is not machine dependent .It can be run any machine with any processor and with any operating system.

7)PORTABLE:
Java programs gives same results on all machines.

8)INTERPRETED:
Java programs are compiled to generate the byte code.This byte code can be downloaded,and interpreted by the interpreter in JVM.
Interpreter is a part of JVM which converts bytecode to machine code.

9)HIGH PERFORMANCE:
Along with interpreter,there is JIT compiler in JVM. JIT:Just in time,JIT compiler increases the speed of execution.

10)MULTITHREADED:
We can create several processes in java,called threads.This is an essential feature to design server side programs.

11)DYNAMIC:
We can develop programs in java which dynamically.


JVM:
Java Virtual Machine(JVM) is a program,that converts byte code instructions into machine code instructions. JVM is system dependent. Java programs are platform independent because they can be executed on any other computer.

SECURITY PROBLEMS FOR DATA ON INTERNET:

1)Eavesdropping:Reading others data illegally.
  sol:encryption/decryption

2)Tampering:Not only reading others data but also modifying it.
  sol:encryption/decryption

3)Impersonation:A person posing as another person on internet.
  sol:Digital signature

4)Virus:Virus is a computer program that causes damage to data,software and hardware of a computer system.
   sol: .class




The first java program keywords explanation: