Reentrantlock learning - Basic Attributes

After simple imitation of fair lock , Yes ReentrantLock The source code of .
The first node Node To understand the properties of .

//  enumeration :  Sharing mode 
static final Node SHARED = new Node();

//  enumeration :  Exclusive mode 
static final Node EXCLUSIVE = null;

 //  Indicates that the current node is in   Cancel the state 
  static final int CANCELLED =  1;

 //  Indicates that the current node needs to wake up   The subsequent nodes 
static final int SIGNAL    = -1;

waitStatus It is mainly through the state to judge the node

        // node Turntable ,  Optional value  (0,SINGAL -1 ,CANCELLED 1
        // 0:  Default state 
        // >0  Cancel the state 
        // == -1 , At present node If it is head Node time , After releasing the lock , Need to wake up his successor nodes 
        volatile int waitStatus;

      //  because node Need to build into  fifo queue ,  therefore  prev  Point to the predecessor node 
      volatile Node prev;

    //  because node Need to build into  fifo queue ,  therefore  next  Point to the successor node 
    volatile Node next;

    //  Current thread 
    volatile Thread thread;

  //  Head node   anytime , The threads corresponding to the head node are all currently locked threads 
   private transient volatile Node head;

    // Blocking queue tail node ,
    private transient volatile Node tail;

    //  According to resources 
    //  Exclusive lock mode :0  Unlocked state  >0  Indicates that it has been locked 
    private volatile int state;

//  In exclusive mode : Represents the thread that currently holds the lock 
    private transient Thread exclusiveOwnerThread;