Returns {@code true} if the process of termination has
commenced but not yet completed. This method may be useful for
debugging. A return of {@code true} reported a sufficient
period after shutdown may indicate that submitted tasks have
ignored or suppressed interruption, or are waiting for I/O,
causing this executor not to properly terminate. (See the
advisory notes for class {@link ForkJoinTask} stating that
tasks should not normally entail blocking operations. But if
they do, they must abort them on interrupt.)
@return {@code true} if terminating but not yet terminated
Returns {@code true} if the process of termination has commenced but not yet completed. This method may be useful for debugging. A return of {@code true} reported a sufficient period after shutdown may indicate that submitted tasks have ignored or suppressed interruption, or are waiting for I/O, causing this executor not to properly terminate. (See the advisory notes for class {@link ForkJoinTask} stating that tasks should not normally entail blocking operations. But if they do, they must abort them on interrupt.)
@return {@code true} if terminating but not yet terminated