JAVA-BASED REAL-TIME PROGRAMMING

3.1.6 Thread interruption and termination
There is much to say about thread termination, but in short there are some
simple rules to follow:
1. Return from the run method terminates the thread. After the run
method (which was called by the thread) returns or runs to its end,
control is back into the system call that started the thread (due to
the call of start). That call then completes by terminating the thread.
Thereafter, calling the isAlive of the terminated thread object returns
false.
2. If one thread wants to terminate another thread, that other thread has
to be prepared to commit suicide. Since there is no predefined methods
for doing this, it has to be accomplished by the programmer, either by
changing some state variable (such as a field/attribute named terminate),
or by interrupting the thread which then (by convention) knows
that it should die whenever interrupted.
3.1. Threads
3. The interrupt method is called in the manner “otherThread.interrupt();”
to interrupt another thread. However, unlike hardware interrupts, the
other thread is not really interrupted; it continues its execution as usual,
except that a predefined internal state variable has registered the interrupt
request.
4. Each thread that should be possible to interrupt has to explicitly test
if it has been interrupted. For this purpose, there is a static method
Thread.interrupted() that returns true if interrupt has been called for
the currently running thread. Note that this method also clears the
interrupt flag. To check if another thread (i.e., not the currently running
one) has been interrupted, isInterrupted() has to be called for that
thread object. That does not effect the interrupted status.
5. If a thread was interrupted when blocked on a blocking system call,
such as sleep, it is scheduled immediately for execution but throwing an
InterruptedException. In this case the interrupted flag is not set, but
by catching the InterruptedException we can determine that the thread
was interrupted. Thus, it is the execution of the catch clause that tells
that the thread was interrupted, and the exception handling decides if
the thread should resume its work or terminate (by returning from run).
6. In accordance with the previous item, if a thread already has been interrupted
when a system call (that throws InterruptedException) is issued,
the exception is thrown immediately without blocking.
Due to these rules, the standard way of implementing a thread is to have a
run method looking like:
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