- JMV is a engine that provides runtime environment to drive the Java Code or applications. It converts Java bytecode into machines language. JVM is a part of Java Run Environment (JRE).
- In other programming languages, the compiler produces machine code for a particular system. However, Java compiler produces code for a Virtual Machine known as Java Virtual MMachine.
working:
- First, Java code is complied into bytecode. This bytecode gets interpreted on different machines
- Between host system and Java source, Bytecode is an intermediary language.
- JVM is responsible for allocating memory space.
JVM architecture :
1) ClassLoader:
The class loader is a subsystem used for loading class files. It performs three major functions viz. Loading, Linking, and Initialization.
2) Method Area:
JVM Method Area stores class structures like metadata, the constant runtime pool, and the code for methods.
3) Heap:
All the Objects, their related instance variables, and arrays are stored in the heap. This memory is common and shared across multiple threads.
4) JVM language Stacks:
Java language Stacks store local variables, and it’s partial results. Each thread has its own JVM stack, created simultaneously as the thread is created. A new frame is created whenever a method is invoked, and it is deleted when method invocation process is complete.
5) PC Registers:
PC register store the address of the Java virtual machine instruction which is currently executing. In Java, each thread has its separate PC register.
6) Native Method Stacks:
Native method stacks hold the instruction of native code depends on the native library. It is written in another language instead of Java.
7) Execution Engine:
It is a type of software used to test hardware, software, or complete systems. The test execution engine never carries any information about the tested product.
8) Native Method interface:
The Native Method Interface is a programming framework. It allows Java code which is running in a JVM to call by libraries and native applications.
9) Native Method Libraries:
Native Libraries is a collection of the Native Libraries(C, C++) which are needed by the Execution Engine
