private final Arithmetic arithmetic;

    public ForwardingArithmetic(Arithmetic arithmetic) {
      this.arithmetic = arithmetic;
    }

    @Override
    public int add(int a, int b) {
      return arithmetic.add(a, b);
    }

    @Override
    public int minus(int a, int b) {
      return arithmetic.minus(a, b);
    }

    @Override
    public String toString() {

      doThrow(s);
    }

    public void twoNullableArgsThrowsSecondArg(@Nullable String s, @Nullable Integer i) {
      doThrow(i);
    }

    public static void staticOneArg(String s) {
      checkNotNull(s);
    }

    public static void staticOneNullableArg(@Nullable String s) {}

  private final NavigableMap<K, V> delegate;

  public SafeTreeMap() {
    this(new TreeMap<K, V>());
  }

  public SafeTreeMap(Comparator<? super K> comparator) {
    this(new TreeMap<K, V>(comparator));
  }

  public SafeTreeMap(Map<? extends K, ? extends V> map) {
    this(new TreeMap<K, V>(map));
  }

  public SafeTreeMap(SortedMap<K, ? extends V> map) {
    this(new TreeMap<K, V>(map));
  }

  private final NavigableMap<K, V> delegate;

  public SafeTreeMap() {
    this(new TreeMap<K, V>());
  }

  public SafeTreeMap(Comparator<? super K> comparator) {
    this(new TreeMap<K, V>(comparator));
  }

  public SafeTreeMap(Map<? extends K, ? extends V> map) {
    this(new TreeMap<K, V>(map));
  }

  public SafeTreeMap(SortedMap<K, ? extends V> map) {
    this(new TreeMap<K, V>(map));
  }

  }

  @Override
  public boolean isEmpty() {
    return delegate.isEmpty();
  }

  @Override
  public Iterator<E> iterator() {
    return delegate.iterator();
  }

  @Override
  public E last() {
    return delegate.last();
  }

  @Override
  public @Nullable E lower(E e) {
    return delegate.lower(checkValid(e));
  }

  @Override
  public @Nullable E pollFirst() {

    public ExceptionWithManyConstructors() {}

    public ExceptionWithManyConstructors(Integer i) {}

    public ExceptionWithManyConstructors(Throwable a) {}

    public ExceptionWithManyConstructors(Throwable a, Throwable b) {}

    public ExceptionWithManyConstructors(String s, Throwable b) {
      usedExpectedConstructor = true;
    }

    public ExceptionWithManyConstructors(Throwable a, Throwable b, Throwable c) {}

    // for testing SortedSet and SortedMap methods
    public static final String BEFORE_FIRST = "\0";
    public static final String BEFORE_FIRST_2 = "\0\0";
    public static final String MIN_ELEMENT = "a";
    public static final String AFTER_LAST = "z";
    public static final String AFTER_LAST_2 = "zz";
  }

  public static class Chars extends SampleElements<Character> {
    public Chars() {

    // for testing SortedSet and SortedMap methods
    public static final String BEFORE_FIRST = "\0";
    public static final String BEFORE_FIRST_2 = "\0\0";
    public static final String MIN_ELEMENT = "a";
    public static final String AFTER_LAST = "z";
    public static final String AFTER_LAST_2 = "zz";
  }

  public static class Chars extends SampleElements<Character> {
    public Chars() {

  }

  public void testOf() {
    assertEquals("training", Optional.of("training").get());
  }

  public void testOf_null() {
    try {
      Optional.of(null);
      fail();
    } catch (NullPointerException expected) {
    }
  }

  public void testFromNullable() {
    Optional<String> optionalName = Optional.fromNullable("bob");
    assertEquals("bob", optionalName.get());
  }

  public static final Integer zero = 0;
  public static final Integer one = 1;
  public static final Integer two = 2;
  public static final Integer three = 3;
  public static final Integer four = 4;
  public static final Integer five = 5;
  public static final Integer six = 6;
  public static final Integer seven = 7;
  public static final Integer eight = 8;
  public static final Integer nine = 9;