* Double#POSITIVE_INFINITY POSITIVE_INFINITY} sort to the beginning and the end of the dataset, as
 * you would expect.
 *
 * <p>If required to do a weighted average between an infinity and a finite value, or between an
 * infinite value and itself, the infinite value is returned. If required to do a weighted average
 * between {@link Double#NEGATIVE_INFINITY NEGATIVE_INFINITY} and {@link Double#POSITIVE_INFINITY

 * the current thread leaves the monitor cleanly:
 *
 * <pre>{@code
 * if (monitor.tryEnter()) {
 *   try {
 *     // do things while occupying the monitor
 *   } finally {
 *     monitor.leave();
 *   }
 * } else {
 *   // do other things since the monitor was not available
 * }
 * }</pre>
 *
 * <h2>Comparison with {@code synchronized} and {@code ReentrantLock}</h2>
 *

  }

  /**
   * Verifies that a collection is immutable.
   *
   * <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>

 *       platforms.
 *   <li>All threads generated must be joined inside each test case method (or {@code fail} to do
 *       so) before returning from the method. The {@code joinPool} method can be used to do this
 *       when using Executors.
 * </ol>
 *
 * <p><b>Other notes</b>
 *
 * <ul>

   *
   * @throws IllegalArgumentException if {@code a < 0} or {@code b < 0}
   */
  public static long gcd(long a, long b) {
    /*
     * The reason we require both arguments to be >= 0 is because otherwise, what do you return on
     * gcd(0, Long.MIN_VALUE)? BigInteger.gcd would return positive 2^63, but positive 2^63 isn't an
     * int.
     */
    checkNonNegative("a", a);
    checkNonNegative("b", b);
    if (a == 0) {

    checkSha1("b617318655057264e28bc0b6fb378c8ef146be00", key, data);
  }

  public void testRfc2202_hmacSha1_case2() {
    byte[] key = "Jefe".getBytes(UTF_8);
    String data = "what do ya want for nothing?";

    checkSha1("effcdf6ae5eb2fa2d27416d5f184df9c259a7c79", key, data);
  }

  public void testRfc2202_hmacSha1_case3() {
    byte[] key = fillByteArray(20, 0xaa);

   * containing one element (the given set itself).
   *
   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
   * safe to do so. The exact circumstances under which a copy will or will not be performed are
   * undocumented and subject to change.
   *
   * <p>This method is not type-safe, as it may be called on elements that are not mutually

    return Platform.emptyToNull(string);
  }

  /**
   * Returns {@code true} if the given string is null or is the empty string.
   *
   * <p>Consider normalizing your string references with {@link #nullToEmpty}. If you do, you can
   * use {@link String#isEmpty()} instead of this method, and you won't need special null-safe forms
   * of methods like {@link String#toUpperCase} either. Or, if you'd like to normalize "in the other

      Preconditions.checkNotNull(executor, "Executor was null.");

      RunnableExecutorPair newHead = new RunnableExecutorPair(runnable, executor);
      RunnableExecutorPair oldHead;
      do {
        oldHead = head;
        if (oldHead == null) {
          // If runnables == null then execute() has been called so we should just execute our
          // listener immediately.
          newHead.execute();

      }
    } else { // non-empty list, insert before nextSibling
      /*
       * requireNonNull is safe as long as callers pass a nextSibling that (a) has the same key and
       * (b) is present in the multimap. (And they do, except maybe in case of concurrent
       * modification, in which case all bets are off.)
       */
      KeyList<K, V> keyList = requireNonNull(keyToKeyList.get(key));
      keyList.count++;