JVM’s structure

The structure of the JVM can be described in terms of its runtime data structure in memory and the two subsystems that use the runtime data – the classloader and the execution engine.

Runtime data areas

Each of the runtime data areas of JVM memory belongs to one of two categories:

• Shared areas, which include the following:
  • Method area: Class metadata, static fields, and method bytecode
  • Heap area: Objects (states)
• Unshared areas that are dedicated to a particular application thread, which include the following:
  • Java stack: Current and caller frames, with each frame keeping the state of Java (non-native) method invocation:
    1. Values of local variables
    2. Method parameter values
    3. Values of operands for intermediate calculations (operand stack)
    4. Method return value (if any)
• PC register: The next instruction to execute
• Native method stack: The state of the native method invocations

We have already discussed that a programmer must be careful...