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7.4 JVM Shutdown - Coggle Diagram

- - - - Access to state must be synchronized.
  - - - When or even if finalizers run.
    - - Use finally blocks.
      - Use explicit close() methods.
- - - - JVM may run finalizers if runFinalizersOnExit is true.
      - JVM halts.
    - - Stop or interrupt running threads.
      - Wait forever if hooks/finalizers hang → may need abrupt shutdown.
  - - - Use synchronization for shared data.
      - Avoid deadlocks.
    - - About application state or shutdown reason.
    - - To not delay JVM termination.
    - - Delete temp files.
      - Clean up non-OS-managed resources.
  - - - A single shutdown hook for all services.
      - Sequential execution of shutdown actions.
    - - Avoid race conditions and deadlocks.
      - Ensure correct order based on service dependencies.
- - - - Helper threads that should not prevent JVM shutdown.
    - - All JVM-created threads (like GC) are daemon except main thread.
      - New threads inherit daemon status of their parent.
    - - If only daemon threads remain → JVM initiates orderly shutdown.
      - Daemon threads are abandoned abruptly:
        
        finally blocks not executed.
        
        Stacks not unwound.
- - - - Last normal (non-daemon) thread terminates.
      - System.exit() is called.
      - Platform-specific means (e.g., SIGINT, Ctrl-C).
  - - - Runtime.halt().
      - Killing JVM process (SIGKILL).