Overview of java 

What is java technology

java technology is:
1) A programming language
2) A development environment
3) An application environment
4) A deployement environment

Applets and applications:
Applets are those which requires an web browser to execute and basiclly which contains three files .java->.class->.html

But Applictions are those which not require an web browser and basically it contains two files .java->.class.It is standalone program and which run on client machine

Features of Java technology:
1.The JVM
2.Garbage Collection
3.The JRE
4.JVM tool interface

JVM: It is an imaginary machine that is implemented  by emulating it on real machine.code for jvm is stored in .class file.
Tasks of JVM:
i)Loads code: Performed by the class loader
ii)Verify code:Performed by the bytecode verifier
iii)Execute code:Performed by the run time interpreter

Garbage Collection:As we know that allocated memory space no longer needed should be deallocated.In oter language  deallocation is Programmer's responsibility.but java programming language provides the system level thread to keep track of memory location.Garbage collection has following charactristics:
i)Checks for and frees memory no longer needed
ii)It is done by automatically