}

  public void testNotNull_apply() {
    Predicate<@Nullable Integer> notNull = Predicates.notNull();
    assertFalse(notNull.apply(null));
    assertTrue(notNull.apply(1));
  }

  public void testNotNull_equality() {
    new EqualsTester()
        .addEqualityGroup(Predicates.notNull(), Predicates.notNull())
        .addEqualityGroup(Predicates.isNull())
        .testEquals();
  }

  }

  public void testNotNull_apply() {
    Predicate<@Nullable Integer> notNull = Predicates.notNull();
    assertFalse(notNull.apply(null));
    assertTrue(notNull.apply(1));
  }

  public void testNotNull_equality() {
    new EqualsTester()
        .addEqualityGroup(Predicates.notNull(), Predicates.notNull())
        .addEqualityGroup(Predicates.isNull())
        .testEquals();
  }

        return "Predicates.isNull()";
      }
    },
    /** @see Predicates#notNull() */
    NOT_NULL {
      @Override
      public boolean apply(@CheckForNull Object o) {
        return o != null;
      }

      @Override
      public String toString() {
        return "Predicates.notNull()";
      }
    };

    @SuppressWarnings("unchecked") // safe contravariant cast

        return "Predicates.isNull()";
      }
    },
    /** @see Predicates#notNull() */
    NOT_NULL {
      @Override
      public boolean apply(@CheckForNull Object o) {
        return o != null;
      }

      @Override
      public String toString() {
        return "Predicates.notNull()";
      }
    };

    @SuppressWarnings("unchecked") // safe contravariant cast

   * throws a {@link NullPointerException}.
   *
   * <p>To find the first non-null element in an iterable, use {@code Iterables.find(iterable,
   * Predicates.notNull())}. For varargs, use {@code Iterables.find(Arrays.asList(a, b, c, ...),
   * Predicates.notNull())}, static importing as necessary.
   *
   * <p><b>Note:</b> if {@code first} is represented as an {@link Optional}, this can be

   * throws a {@link NullPointerException}.
   *
   * <p>To find the first non-null element in an iterable, use {@code Iterables.find(iterable,
   * Predicates.notNull())}. For varargs, use {@code Iterables.find(Arrays.asList(a, b, c, ...),
   * Predicates.notNull())}, static importing as necessary.
   *
   * <p><b>Note:</b> if {@code first} is represented as an {@link Optional}, this can be

   */

  /** Monitor guarding all access */
  final Monitor monitor;

  /** Guard for waiting takes */
  private final Monitor.Guard notEmpty;

  /** Guard for waiting puts */
  private final Monitor.Guard notFull;

  // Internal helper methods

  /** Circularly increment i. */
  final int inc(int i) {
    return (++i == items.length) ? 0 : i;
  }

  /**

   */

  /** Monitor guarding all access */
  final Monitor monitor;

  /** Guard for waiting takes */
  private final Monitor.Guard notEmpty;

  /** Guard for waiting puts */
  private final Monitor.Guard notFull;

  // Internal helper methods

  /** Circularly increment i. */
  final int inc(int i) {
    return (++i == items.length) ? 0 : i;
  }

  /**