The Java Virtual Machine (JVM) is a software platform that executes Java code and provides a runtime environment for Java applications. It operates on the principle of Write Once, Run Anywhere (WORA).
The JVM is composed of the following components:
Class Loader: Responsible for loading Java classes into the JVM.
Execution Engine: The main component of the JVM, responsible for executing Java bytecode and providing memory management and garbage collection services.
Java Heap: The memory space where objects and instances of classes are stored and managed.
Java Stack: A per-thread stack data structure that stores frames, which contain method calls and their parameters.
Program Counter Register: A register that keeps track of the current instruction being executed by the JVM.
Native Method Stack: A stack for executing native methods written in languages other than Java.
Method Area: A shared memory space where class-level information such as constant pool and class variables are stored.
Register Set: A set of machine-level registers used to hold intermediate values and pointers during the execution of a method.
The JVM also provides several services such as memory management, thread synchronization, security, and others to support the execution of Java applications.