try {
      iterator.next();
      fail("no exception thrown");
    } catch (NoSuchElementException expected) {
    }
    try {
      iterator.previous();
      fail("no exception thrown");
    } catch (NoSuchElementException expected) {
    }
    try {
      iterator.remove();
      fail("no exception thrown");
    } catch (UnsupportedOperationException expected) {
    }

    try {
      iterator.next();
      fail("no exception thrown");
    } catch (NoSuchElementException expected) {
    }
    try {
      iterator.previous();
      fail("no exception thrown");
    } catch (NoSuchElementException expected) {
    }
    try {
      iterator.remove();
      fail("no exception thrown");
    } catch (UnsupportedOperationException expected) {
    }

 * correctly (that is, whether its <i>preconditions</i> were met).
 *
 * <p>If the precondition is not met, the {@code Preconditions} method throws an unchecked exception
 * of a specified type, which helps the method in which the exception was thrown communicate that
 * its caller has made a mistake. This allows constructs such as
 *
 * <pre>{@code
 * public static double sqrt(double value) {
 *   if (value < 0) {

   * IllegalArgumentException} if passed a {@code fromKey} less than an earlier {@code fromKey}.
   * However, this method doesn't throw an exception in that situation, but instead keeps the
   * original {@code fromKey}. Similarly, this method keeps the original {@code toKey}, instead of
   * throwing an exception, if passed a {@code toKey} greater than an earlier {@code toKey}.
   */
  @Override

 * correctly (that is, whether its <i>preconditions</i> were met).
 *
 * <p>If the precondition is not met, the {@code Preconditions} method throws an unchecked exception
 * of a specified type, which helps the method in which the exception was thrown communicate that
 * its caller has made a mistake. This allows constructs such as
 *
 * <pre>{@code
 * public static double sqrt(double value) {
 *   if (value < 0) {

    }
  }

  public void testToStringImplWithNullKeys() throws Exception {
    Map<@Nullable String, String> hashmap = Maps.newHashMap();
    hashmap.put("foo", "bar");
    hashmap.put(null, "baz");

    assertEquals(hashmap.toString(), Maps.toStringImpl(hashmap));
  }

  public void testToStringImplWithNullValues() throws Exception {
    Map<String, @Nullable String> hashmap = Maps.newHashMap();

    }
  }

  public void testToStringImplWithNullKeys() throws Exception {
    Map<@Nullable String, String> hashmap = Maps.newHashMap();
    hashmap.put("foo", "bar");
    hashmap.put(null, "baz");

    assertEquals(hashmap.toString(), Maps.toStringImpl(hashmap));
  }

  public void testToStringImplWithNullValues() throws Exception {
    Map<String, @Nullable String> hashmap = Maps.newHashMap();

    TypeToken<List<String>> b = new TypeToken<List<String>>() {};
    assertEquals(a, b);
  }

  public <T> void testVariableTypeTokenNotAllowed() {
    /*
     * We'd use assertThrows here, but that causes no exception to be thrown under Java 8,
     * presumably because the ThrowingRunnable lambda triggers some kind of bug in Java 8's
     * reflection implementation.
     */
    try {
      new TypeToken<T>() {};
      fail();

   * IllegalArgumentException} if passed a {@code fromKey} less than an earlier {@code fromKey}.
   * However, this method doesn't throw an exception in that situation, but instead keeps the
   * original {@code fromKey}. Similarly, this method keeps the original {@code toKey}, instead of
   * throwing an exception, if passed a {@code toKey} greater than an earlier {@code toKey}.
   */
  @Override

    TypeToken<List<String>> b = new TypeToken<List<String>>() {};
    assertEquals(a, b);
  }

  public <T> void testVariableTypeTokenNotAllowed() {
    /*
     * We'd use assertThrows here, but that causes no exception to be thrown under Java 8,
     * presumably because the ThrowingRunnable lambda triggers some kind of bug in Java 8's
     * reflection implementation.
     */
    try {
      new TypeToken<T>() {};
      fail();