Question

What is the difference between a parked thread and a waiting thread in java ? I’ve a jboss core dump and analysing it is showing a lot of parked threads.

Answer 1

Look at Javadoc the park() method:

Disables the current thread for thread scheduling purposes unless the
permit is available. If the permit is available then it is consumed
and the call returns immediately; otherwise the current thread becomes
disabled for thread scheduling purposes and lies dormant until one of
three things happens:

Some other thread invokes unpark with the current thread as the
target; or Some other thread interrupts the current thread; or The
call spuriously (that is, for no reason) returns. This method does not
report which of these caused the method to return. Callers should
re-check the conditions which caused the thread to park in the first
place. Callers may also determine, for example, the interrupt status
of the thread upon return.

So a parked thread is a thread blocked using LockSupport.park().