- A specification where working of Java Virtual Machine is specified. But implementation provider is independent to choose the algorithm. Its implementation has been provided by Sun and other companies.
- An implementation its implementation is known as JRE (Java Runtime Environment)
- Run time Instance Whenever you write java command on the command prompt to run the java class, and instance of JVM is created.
- Loads code
- Verifies Code
- Executes Code
- Provides runtime environment
- Memory Area
- Class file format
- Register set
- Garbage-collected heap
- Fatal error reporting etc.
- Class loader: Class loader is a subsystem of JVM that is used to load class files.
- Class (Method) Area: Class (Method) Area stores per-class structures such as the runtime constant pool, field and method data, the code for methods.
- Heap: It is the runtime data area in which objects are allocated.
- Stack: Java Stack stores frames. It holds local variables and partial results, and plays a part in method invocation and return. Each thread has a private JVM stack, created at the same time as thread. A new frame is created each time a method is invoked. A frame is destroyed when its method invocation completes.
- Program Counter Register: PC (program counter) register. It contains the address of the Java virtual machine instruction currently being executed.
- Native Method Stack: It contains all the native methods used in the application.
- Execution Engine:
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