@Override
   public Object[] toArray() {
      return new Object[0];
   }
@Test
   public void testToArray1() throws Exception {
      Object[] array = es.toArray(new Integer[1]);
      assertEquals(1, array.length);
      assertEquals(null, array[0]);

      array = es.toArray(new Integer[0]);
      assertEquals(0, array.length);
   }