java - Thread.stop() - deprecated

Question

Why is Thread.stop() deprecated in Java? On their website, I see the following:

Why is Thread.stop deprecated?

Because it is inherently unsafe. Stopping a thread causes it to unlock all the monitors that it has locked. (The monitors are unlocked as the ThreadDeath exception propagates up the stack.) If any of the objects previously protected by these monitors were in an inconsistent state, other threads may now view these objects in an inconsistent state. Such objects are said to be damaged. When threads operate on damaged objects, arbitrary behavior can result. This behavior may be subtle and difficult to detect, or it may be pronounced. Unlike other unchecked exceptions, ThreadDeath kills threads silently; thus, the user has no warning that his program may be corrupted. The corruption can manifest itself at any time after the actual damage occurs, even hours or days in the future.

I don't understand what they mean by "monitors". Regardless, my question is if Thread.stop() should not be called then how should a Java thread be stopped?

Answer 1

You asked:

My question is if theres no way to stop a thread in Java then how to stop a thread?

The Answer: In Java there's no clean, quick or reliable way to stop a thread.

Thread termination is not so straight forward. A running thread, often called by many writers as a light-weight process, has its own stack and is the master of its own destiny (well daemons are). It may own files and sockets. It may hold locks. Abrupt Termination is not always easy: Unpredictable consequences may arise if the thread is in the middle of writing to a file and is killed before it can finish writing. Or what about the monitor locks held by the thread when it is shot in the head?

Instead, Threads rely on a cooperative mechanism called Interruption. This means that Threads could only signal other threads to stop, not force them to stop.

To stop threads in Java, we rely on a co-operative mechanism called Interruption. The concept is very simple. To stop a thread, all we can do is deliver it a signal, aka interrupt it, requesting that the thread stops itself at the next available opportunity. That’s all. There is no telling what the receiver thread might do with the signal: it may not even bother to check the signal; or even worse ignore it.

Source: https://codeahoy.com/java/How-To-Stop-Threads-Safely/