AQS源码解读（ReentrankLock的公平锁和非公平锁）

1. 构建Debug代码：

    1 package com.hl.interview.lock;
    2
    3 import java.util.Scanner;
    4 import java.util.concurrent.locks.Lock;
    5 import java.util.concurrent.locks.LockSupport;
    6 import java.util.concurrent.locks.ReentrantLock;
    7
    8 /**
    9  * @author Hl
   10  * @create 2021/2/20 9:36
   11  */
   12 public class AQS {
   13     static Lock lock = new ReentrantLock();
   14     volatile static int flag = 0;
   15
   16     public static void main(String[] args) {
   17         Scanner scanner = new Scanner(System.in);
   18         Thread a = new Thread(() -> {
   19             lock.lock();
   20             try {
   21                 System.out.println(Thread.currentThread().getName() + "先占用了");
   22                 LockSupport.park();
   23             } finally {
   24                 lock.unlock();
   25             }
   26         }, "A");
   27
   28         Thread b = new Thread(() -> {
   29             LockSupport.park();
   30             // 下面是断点处
   31             System.out.println("开始B线程");
   32             lock.lock();
   33             try {
   34                 System.out.println(Thread.currentThread().getName() + "抢占");
   35                 LockSupport.park();
   36             } finally {
   37                 lock.unlock();
   38             }
   39         }, "B");
   40
   41         Thread c = new Thread(() -> {
   42             LockSupport.park();
   43               // 下面是断点处
   44             System.out.println("开始C线程");
   45             lock.lock();
   46             try {
   47                 System.out.println(Thread.currentThread().getName() + "抢占");
   48                 LockSupport.park();
   49             } finally {
   50                 lock.unlock();
   51             }
   52         }, "C");
   53         a.start();
   54         b.start();
   55         c.start();
   56         System.out.print("请输入一个数:\t" );
   57         while (scanner.hasNextInt()) {
   58             System.out.print("请输入一个数:\t" );
   59             flag = scanner.nextInt();
   60             System.out.println();
   61             if (flag == 1) {
   62                 System.out.println("释放了A线程");
   63                 LockSupport.unpark(a);
   64             } else if (flag == 2) {
   65                 System.out.println("释放了B线程");
   66                 LockSupport.unpark(b);
   67             } else if (flag == 3) {
   68                 System.out.println("释放了C线程");
   69                 LockSupport.unpark(c);
   70             } else {
   71                 System.out.println("退出了程序");
   72                 break;
   73             }
   74         }
   75     }
   76 }

2. Debug所有断点处
   
3. 流程图，个人理解，有些地方理解的不太透彻望包涵
   

流程图地址