code: @SuppressWarnings("unchecked") @Test public void testExecuteSupplier(){
    ServiceExecutor executor=new StampedLockServiceExecutor();
    Object expected=new Object();
    Supplier<Object> executeTask=mock(Supplier.class);
    when(executeTask.get()).thenReturn(expected);
    Optional<Object> result=executor.execute(executeTask);
    assertTrue(result.isPresent());
    assertSame(expected,result.get());
    reset(executeTask);
    Runnable closeTask=mock(Runnable.class);
    executor.close(closeTask);
    verify(closeTask).run();
    reset(closeTask);
    executor.close(closeTask);
    verify(closeTask,never()).run();
    result=executor.execute(executeTask);
    assertFalse(result.isPresent());
  }
  