As per Java Documentation, the park() method has the following usage:
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.
To put it in simple terms, a parked thread is a thread that is blocked using LockSupport.park(). For further reference, click here
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