props.save(System.err);
        System.err.println("=====");

        props.put("key2", props.get("key2"));
        props.put("key3", "foo");
        props.save(System.err);
        System.err.println("=====");
    }

    @Test
    public void testJavaUtilPropertiesCompatibility() throws Exception {
        MavenProperties properties = new MavenProperties();

    String key1 = "QED";
    String key2 = "R&D";
    assertThat(key1.hashCode()).isEqualTo(key2.hashCode());
    ImmutableMap<String, Integer> map =
        ImmutableMap.<String, Integer>builder()
            .put(key1, 1)
            .put(key2, 2)
            .put(key1, 3)
            .put(key2, 4)
            .buildKeepingLast();
    assertMapEquals(map, key1, 3, key2, 4);
  }

    String key1 = "QED";
    String key2 = "R&D";
    assertThat(key1.hashCode()).isEqualTo(key2.hashCode());
    ImmutableMap<String, Integer> map =
        ImmutableMap.<String, Integer>builder()
            .put(key1, 1)
            .put(key2, 2)
            .put(key1, 3)
            .put(key2, 4)
            .buildKeepingLast();
    assertMapEquals(map, key1, 3, key2, 4);
  }