@Override public V get(Object o) {
    if (o == null) return null; // null keys are not allowed
    int i = arrayIndexOfKey(o);
    return i != -1 ? value(i + 1) : null;
  }
@Test void equalValues() {
    array[0] = "1";
    array[1] = "1";
    array[2] = "2";
    array[3] = "2";
    array[4] = "3";
    array[5] = "3";

    Map<String, String> map = builder.build(array);
    assertSize(map, 3);
    assertBaseCase(map);

    assertThat(map).containsOnly(
        entry("1", "1"),
        entry("2", "2"),
        entry("3", "3")
    );
    assertThat(map).hasToString(
        "UnsafeArrayMap{1=1,2=2,3=3}"
    );

    assertThat(map.get("1")).isEqualTo("1");
    assertThat(map.get("2")).isEqualTo("2");
    assertThat(map.get("3")).isEqualTo("3");
  }