@Test
public void equals_() {

    DefaultMapEntry<String, Object> e1 = new DefaultMapEntry<String, Object>(null, null);
    DefaultMapEntry<String, Object> e2 = new DefaultMapEntry<String, Object>("hello", "baobao");
    assertTrue(e1.equals(entry1));
    assertTrue(e2.equals(entry2));
    assertTrue(e1.equals(e1));
    assertFalse(e1.equals(null));
    assertFalse(e1.equals(""));
}