Threads - The Java Programming Language - page 542

Thread 2
Interrupting the thread advises it that you want it to pay attention, usu-
ally to get it to halt execution. An interrupt does not force the thread
to halt, although it will interrupt the slumber of a sleeping or waiting
thread.
Interruption is also useful when you want to give the running thread
some control over when it will handle an event. For example, a display
update loop might need to access some database information using a
transaction and would prefer to handle a user's "cancel" after waiting
until that transaction completes normally. The user-interface thread
might implement a "Cancel" button by interrupting the display thread to
give the display thread that control. This approach will work well as long
as the display thread is well behaved and checks at the end of every
transaction to see whether it has been interrupted, halting if it has.
The following methods relate to interrupting a thread: interrupt , which
sends an interrupt to a thread; isInterrupted , which tests whether a
thread has been interrupted; and interrupted , a static method that tests
whether the current thread has been interrupted and then clears the
"interrupted" state of the thread. The interrupted state of a thread can
be cleared only by that threadthere is no way to "uninterrupt" another
thread. There is generally little point in querying the interrupted state
of another thread, so these methods tend to be used by the current
thread on itself. When a thread detects that it has been interrupted, it
often needs to perform some cleanup before actually responding to the
interrupt. That cleanup may involve actions that could be affected if the
thread is left in the inter rupted state, so the thread will test and clear
its interrupted state using interrupted .