[Java] Java线程公平锁和非公平锁的差异讲解

/**
   * fair version of tryacquire. don't grant access unless
   * recursive call or no waiters or is first.
   **/
  protected final boolean tryacquire(int acquires) {
    final thread current = thread.currentthread();
    int c = getstate();
    if (c == 0) {
    if (!hasqueuedpredecessors() &&
      compareandsetstate(0, acquires)) {
      setexclusiveownerthread(current);
      return true;
    }
    }
    else if (current == getexclusiveownerthread()) {
    int nextc = c + acquires;
    if (nextc < 0)
      throw new error("maximum lock count exceeded");
    setstate(nextc);
    return true;
    }
    return false;
  }