Primary Goals of the Java Technology

Java Technology provides the following :

• A language that is easy to program  because it :

         1: Eliminates  many pitfalls of other languages,such as pointer arithmetic and memory management that effect the robustness of the code.

          2: Is object-oriented to help you visualize the program in real-life terms 

          3: Enables you to streamline code

• An interpreter environment resulting in the following benefits :

          1: Speed of development -Reduces the compile-link-load-test cycle

        2: Code portability -Enables you to write code that can be run on multiple operating systems on any certified JVM

•  A way for programs to run more than one thread of activity
• It means to change programs dynamically during  their runtime life by enabling them to download code modules 
• It means of ensuring security by checking loaded code modules

The java technology architecture uses the following features to fulfill the previously listed goals :

• The JVM
• Garbage collection 
• The JRE 
• JVM tool interface

JVM is an imaginary machine that is implemented by emulating it in software on a real machine.It provides the hardware platform specifications to which you compile all Java Technology code .
There are three main task performed by JVM:
1:Loads code- performed by the class loader
2:Verifies code-performed by the bytecode verifier
3:Executes code-performed by the rumtime intepreter

The Class Loader:
The class loader loads all classes needed for the execution of a program.The class loader adds security by separating the namespace for the classes of the local file system from those imported from network sources.

The Bytecode Verifier:
Java software code passes several tests before running on your machines.The JVM puts the code though a bytecode verifier that tests the format of code fragments and checks code fragments for illegal code,which is code that forges pointers,violates access rights on objects or attempts to change the object type.