}

  public void testPowerSetIteration_manual() {
    ImmutableSet<Integer> elements = ImmutableSet.of(1, 2, 3);
    Set<Set<Integer>> powerSet = powerSet(elements);
    // The API doesn't promise this iteration order, but it's convenient here.
    Iterator<Set<Integer>> i = powerSet.iterator();
    assertEquals(ImmutableSet.of(), i.next());
    assertEquals(ImmutableSet.of(1), i.next());

   * use the copy.
   *
   * <p><b>Warning:</b> {@code predicate} must be <i>consistent with equals</i>, as documented at
   * {@link Predicate#apply}. Do not provide a predicate such as {@code
   * Predicates.instanceOf(ArrayList.class)}, which is inconsistent with equals. (See {@link
   * Iterables#filter(Iterable, Class)} for related functionality.)
   *

  }

  // Constructors

  /**
   * Constructor for use by subclasses. When subclassing, you may want to override {@code
   * toString()} to provide a useful description.
   */
  protected CharMatcher() {}

  // Abstract methods

  /** Determines a true or false value for the given character. */
  public abstract boolean matches(char c);

 * Futures#catching(ListenableFuture, Class, com.google.common.base.Function,
 * java.util.concurrent.Executor) Futures.catching}.
 *
 * <p>This class implements all methods in {@code ListenableFuture}. Subclasses should provide a way
 * to set the result of the computation through the protected methods {@link #set(Object)}, {@link
 * #setFuture(ListenableFuture)} and {@link #setException(Throwable)}. Subclasses may also override

   * copy.
   *
   * <p><b>Warning:</b> {@code keyPredicate} must be <i>consistent with equals</i>, as documented at
   * {@link Predicate#apply}. Do not provide a predicate such as {@code
   * Predicates.instanceOf(ArrayList.class)}, which is inconsistent with equals.
   *
   * @since 11.0
   */

  }

  // Constructors

  /**
   * Constructor for use by subclasses. When subclassing, you may want to override {@code
   * toString()} to provide a useful description.
   */
  protected CharMatcher() {}

  // Abstract methods

  /** Determines a true or false value for the given character. */
  public abstract boolean matches(char c);