* @return true if the user can login, false otherwise
     * @throws UnsupportedOperationException always thrown as this method is not supported
     */
    @Override
    public boolean checkUserLoginable(final LoginCredential credential) {
        throw new UnsupportedOperationException("checkUserLoginable is not supported.");
    }

    /**

  public final void clear() {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the {@code RangeMap} unmodified.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @Deprecated
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")

      fail("Expected UnsupportedOperationException or NullPointerException.");
    } catch (UnsupportedOperationException | NullPointerException e) {
      // Expected.
    }
    assertInvariants(map);

    try {
      entrySet.addAll(singleton((Entry<K, V>) entryToAdd));
      fail("Expected UnsupportedOperationException or NullPointerException.");
    } catch (UnsupportedOperationException | NullPointerException e) {

      fail("UnsupportedOperationException expected");
    } catch (UnsupportedOperationException expected) {
    }
    try {
      unmod.addAll(singleton(4));
      fail("UnsupportedOperationException expected");
    } catch (UnsupportedOperationException expected) {
    }
    try {
      unmod.pollFirst();
      fail("UnsupportedOperationException expected");
    } catch (UnsupportedOperationException expected) {

   *
   * @since 12.0
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @CanIgnoreReturnValue
  @Deprecated
  @GwtIncompatible // NavigableSet
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  public final @Nullable E pollFirst() {
    throw new UnsupportedOperationException();
  }

  /**

      fail(message);
    } catch (UnsupportedOperationException expected) {
    }
  }

  private void expectReturnsFalseOrThrows(Target target) {
    String message = Platform.format("retainAll(%s) should return false or throw", target);
    try {
      assertFalse(message, collection.retainAll(target.toRetain));
    } catch (UnsupportedOperationException tolerated) {
    }
  }

        }

        @Override
        public String getPathInfo() {
            throw new UnsupportedOperationException();
        }

        @Override
        public String getPathTranslated() {
            throw new UnsupportedOperationException();
        }

        @Override
        public String getContextPath() {
            throw new UnsupportedOperationException();

   * UnsupportedOperationException."
   */
  abstract void setCountNoCheckReturnValue(E element, int count);

  private void assertSetCountIncreasingFailure(E element, int count) {
    try {
      setCountNoCheckReturnValue(element, count);
      fail("a call to multiset.setCount() to increase an element's count should throw");
    } catch (UnsupportedOperationException expected) {
    }
  }

  public final void clear() {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the {@code RangeMap} unmodified.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @Deprecated
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")

   * <p>A collection is considered immutable if:
   *
   * <ol>
   *   <li>All its mutation methods result in UnsupportedOperationException, and do not change the
   *       underlying contents.
   *   <li>All methods that return objects that can indirectly mutate the collection throw
   *       UnsupportedOperationException when those mutators are called.
   * </ol>
   *
   * @param collection the presumed-immutable collection