JVM Architecture

JVM Architecture

The internal architecture of the JVM is as below:-

1) Class loader:- It loads the .class file into the memory. Then it verifies all the class code and if it finds any suspicious, then the execution is rejected.

2) Class (Method) Area:-It stores all the class code ,code of variables and methods and also all static variables are created in this area.

3) Heap:-It stores all the Objects.

4) Java Thread/Stack:-As we know that method code is stored in method area but while executing the method to store intermediate results it uses stack. Java uses separate thread to execute each method.

A new frame is created each time a method is executed destroyed when its method execution is completes.

5) Program Counter Register:-PC (program counter) register contains the address of the Java virtual machine instruction currently being executed. If there are 3 methods executing then there will be 3 PC registers maintained.

6) Native Method Stack:-Like Java methods execute in java stack, similarly all the native methods execute in native method stack. Example for Native lib is C, C++ functions. The native method lib is connected to JVM through a program called Native method interface.

7) Execution Engine:- It contains of below components:-

1) Interpreter

2) Just-In-Time(JIT) compiler

The java code is executed by both interpreter and JIT compiler simultaneously so that the execution time is reduced and performance is increased. The code that is executed by JIT compiler is called as HOTSPOTS (company).