public boolean isEmpty() {
    return members.size() == 0;
  }
@Test
  public void testIsEmpty() {
    JsonObject o = new JsonObject();
    assertThat(o.isEmpty()).isTrue();

    o.add("Hello", new JsonPrimitive(1));
    assertThat(o.isEmpty()).isFalse();

    o.remove("Hello");
    assertThat(o.isEmpty()).isTrue();
  }