@Test
 public void put_get() throws Exception {
   final StringKeyObjectMap<Integer> map = new StringKeyObjectMap<Integer>();
   Assert.assertNull(map.get("abc"));
   map.put("abc", Integer.valueOf(0));
   Assert.assertEquals(Integer.valueOf(0), map.get("abc"));
 }
 @Test
 public void clear_isEmpty() throws Exception {
   final StringKeyObjectMap<Integer> map = new StringKeyObjectMap<Integer>();
   Assert.assertTrue(map.isEmpty());
   map.put("abc", Integer.valueOf(0));
   Assert.assertFalse(map.isEmpty());
   Assert.assertEquals(Integer.valueOf(0), map.get("abc"));
   map.clear();
   Assert.assertTrue(map.isEmpty());
   Assert.assertNull(map.get("abc"));
 }