ReentrantLock.FairSync::initialTryLock源码笔记

// ReentrantLock.FairSync::initialTryLock
final boolean initialTryLock() {
     Thread current = Thread.currentThread();
     int c = getState();
     // c==0说明当前锁无人获取
     if (c == 0) {
          // hasQueuedThreads()==false说明当前线程排在队首，此时才能进行cas操作，否则不公平
          if (!hasQueuedThreads() && compareAndSetState(0, 1)) {
          setExclusiveOwnerThread(current);
          return true;
          }
     // 锁已经被当前线程获取，这次获取为重入，与Sync::tryLock逻辑一样
     } else if (getExclusiveOwnerThread() == current) {
          if (++c < 0) // overflow
          throw new Error("Maximum lock count exceeded");
          setState(c);
          return true;
     }
     return false;
}