NullPointerTester tester = new NullPointerTester();
    // Necessary until JDK15:
    // https://bugs.openjdk.org/browse/JDK-8202469
    tester.ignore(Equivalence.class.getMethod("wrap", Object.class));

    tester.testAllPublicStaticMethods(Equivalence.class);
    tester.testAllPublicInstanceMethods(Equivalence.equals());
    tester.testAllPublicInstanceMethods(Equivalence.identity());
  }

  private String leave() {
    return "leave";
  }

  public final void testMutualExclusion() throws Exception {
    thread1.callAndAssertReturns(enter());
    thread2.callAndAssertBlocks(enter());
    thread1.callAndAssertReturns(leave());
    thread2.assertPriorCallReturns(enter());
  }

  public final void testTryEnter() throws Exception {
    thread1.callAndAssertReturns(true, tryEnter());

  public static class Chars extends SampleElements<Character> {
    public Chars() {
      // elements aren't sorted, to better test SortedSet iteration ordering
      super('b', 'a', 'c', 'd', 'e');
    }
  }

  public static class Enums extends SampleElements<AnEnum> {
    public Enums() {
      // elements aren't sorted, to better test SortedSet iteration ordering
      super(AnEnum.B, AnEnum.A, AnEnum.C, AnEnum.D, AnEnum.E);
    }
  }

  public static class Chars extends SampleElements<Character> {
    public Chars() {
      // elements aren't sorted, to better test SortedSet iteration ordering
      super('b', 'a', 'c', 'd', 'e');
    }
  }

  public static class Enums extends SampleElements<AnEnum> {
    public Enums() {
      // elements aren't sorted, to better test SortedSet iteration ordering
      super(AnEnum.B, AnEnum.A, AnEnum.C, AnEnum.D, AnEnum.E);
    }
  }

  public void testNullPointers() {
    NullPointerTester tester = new NullPointerTester();
    tester.testAllPublicStaticMethods(Joiner.class);
    tester.testInstanceMethods(Joiner.on(","), NullPointerTester.Visibility.PACKAGE);
    tester.testInstanceMethods(Joiner.on(",").skipNulls(), NullPointerTester.Visibility.PACKAGE);
    tester.testInstanceMethods(

  public void testStringConverter_nullPointerTester() throws Exception {
    Converter<String, TestEnum> converter = Enums.stringConverter(TestEnum.class);
    NullPointerTester tester = new NullPointerTester();
    tester.testAllPublicInstanceMethods(converter);
  }

  @GwtIncompatible // stringConverter
  public void testStringConverter_nullConversions() {

    NullPointerTester tester = new NullPointerTester();
    tester.testAllPublicInstanceMethods(InterfaceDefaultMethodChecksNull.create());
    try {
      tester.testAllPublicInstanceMethods(InterfaceDefaultMethodFailsToCheckNull.create());
    } catch (AssertionError expected) {
      return;
    }
    fail();
  }

  public void testDontAcceptIae() {
    NullPointerTester tester = new NullPointerTester();

  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNulls() {
    NullPointerTester tester = new NullPointerTester();
    tester.testAllPublicInstanceMethods(ADAPTER);
  }

      }
    }
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNullArguments() {
    NullPointerTester tester = new NullPointerTester();
    tester.testAllPublicStaticMethods(CaseFormat.class);
    for (CaseFormat format : CaseFormat.values()) {
      tester.testAllPublicInstanceMethods(format);
    }
  }

  public void testLowerHyphenToLowerHyphen() {

  @CheckForNull
  public V put(K key, @ParametricNullness V value) {
    return super.put(key, value);
  }

  @CanIgnoreReturnValue
  @Override
  @SuppressWarnings("RedundantOverride") // b/192446478: RedundantOverride ignores some annotations.
  // TODO(b/192446998): Remove this override after tools understand nullness better.
  @CheckForNull