/**
 * Static methods for implementing hash-based collections.
 *
 * @author Kevin Bourrillion
 * @author Jesse Wilson
 * @author Austin Appleby
 */
@GwtCompatible
final class Hashing {
  private Hashing() {}

  /*
   * These should be ints, but we need to use longs to force GWT to do the multiplications with
   * enough precision.
   */
  private static final long C1 = 0xcc9e2d51;

   * specific length.
   *
   * <p>For example, if you need 1024-bit hash codes, you could join two {@link Hashing#sha512} hash
   * functions together: {@code Hashing.concatenating(Hashing.sha512(), Hashing.sha512())}.
   *
   * @since 19.0
   */
  public static HashFunction concatenating(
      HashFunction first, HashFunction second, HashFunction... rest) {

   * closed.
   *
   * <p>Usage guidelines for this method:
   *
   * <ul>
   *   <li>Use this method only when calling an API that returns a {@link ListenableFuture} or a
   *       {@code ClosingFuture}. If possible, prefer calling {@link #catching(Class,
   *       ClosingFunction, Executor)} instead, with a function that returns the next value
   *       directly.

    ListenableFuture<Integer> derived =
        catching(primary, Throwable.class, fallback, directExecutor());
    derived.cancel(false);
    assertTrue(primary.isCancelled());
    assertFalse(primary.wasInterrupted());
  }

  // catching() uses a plain Function, so there's no testCatching_resultCancelledAfterFallback().

  // catching() uses a plain Function, so there's no testCatching_nullInsteadOfFuture().

    ListenableFuture<Integer> derived =
        catching(primary, Throwable.class, fallback, directExecutor());
    derived.cancel(false);
    assertTrue(primary.isCancelled());
    assertFalse(primary.wasInterrupted());
  }

  // catching() uses a plain Function, so there's no testCatching_resultCancelledAfterFallback().

  // catching() uses a plain Function, so there's no testCatching_nullInsteadOfFuture().

 *   <li>an {@linkplain Thread#setUncaughtExceptionHandler uncaught exception handler}
 *   <li>a {@linkplain ThreadFactory#newThread backing thread factory}
 * </ul>
 *
 * <p>If no backing thread factory is provided, a default backing thread factory is used as if by
 * calling {@code setThreadFactory(}{@link Executors#defaultThreadFactory()}{@code )}.
 *

   * note that the execution order of all listeners is ultimately chosen by the implementations of
   * the supplied executors.
   *
   * <p>This method is idempotent. Calling it several times in parallel is semantically equivalent
   * to calling it exactly once.
   *
   * @since 10.0 (present in 1.0 as {@code run})
   */
  public void execute() {

   * java.util.TreeMap}).
   *
   * <p>Each method invocation on the set returned by this method results in exactly one method
   * invocation on the backing map or its {@code keySet} view, with one exception. The {@code
   * addAll} method is implemented as a sequence of {@code put} invocations on the backing map.
   *
   * <p>The specified map must be empty at the time this method is invoked, and should not be

   * java.util.TreeMap}).
   *
   * <p>Each method invocation on the set returned by this method results in exactly one method
   * invocation on the backing map or its {@code keySet} view, with one exception. The {@code
   * addAll} method is implemented as a sequence of {@code put} invocations on the backing map.
   *
   * <p>The specified map must be empty at the time this method is invoked, and should not be

 * com.google.common.base.Function, java.util.concurrent.Executor) Futures.transform} and {@link
 * 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