Thread Lifecycle: Priority, Interruption, Factory

Thread priority is a hint, not a promise: the JLS guarantees nothing and modern schedulers mostly ignore it, so never use it for correctness.

interrupt() raises a flag, the thread checks the flag at safe points and decides to stop: it is a polite request, not a forced stop.

stop leaves money half-moved and locks dropped, suspend freezes a thread holding locks and deadlocks everyone else: always use interrupt plus InterruptedException instead.

ThreadGroup is a dead-end from the 1990s: use ExecutorService and structured concurrency, and always name your threads pool-name-thread-N so dumps and logs are readable.

A custom ThreadFactory names, flags, prioritizes, and attaches a crash handler to every pool thread at birth: pass it to the ThreadPoolExecutor constructor so observability starts before the first task runs.