jdk1.5-Lock的使用

今天药忘吃喽~ 2023-07-08 09:19 6阅读 0赞

package com.study.communication;
    
    import java.util.concurrent.locks.Condition;
    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;
    
    class LockRes {
        public String userName;
        public String sex;
        //true生产者线程等待，false消费者线程生产，生产者可以写，消费者变为等待
        public boolean flag = false;
        Lock lock = new ReentrantLock();//jdk1.5并发包lock锁
    }
    
    /**
     * 读
     */
    @SuppressWarnings("Duplicates")
    class LockOut extends Thread {
        LockRes lockRes;
        Condition newCondition;
    
        LockOut(LockRes lockRes, Condition newCondition) {
            this.lockRes = lockRes;
            this.newCondition = newCondition;
        }
    
        @Override
        public void run() {
            int count = 0;
            while (true) {
                try {
                    lockRes.lock.lock();//表示开始上锁
                    if (lockRes.flag) {
                        try {
                            //让线程等待
                            newCondition.await();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                    if (count == 0) {
                        lockRes.userName = "小红";
                        lockRes.sex = "女";
                    } else {
                        lockRes.userName = "小王";
                        lockRes.sex = "男";
                    }
                    count = (count + 1) % 2;
                    lockRes.flag = true;
                    newCondition.signal();//唤醒
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    lockRes.lock.unlock();
                }
    
            }
        }
    }
    
    /**
     * 写
     */
    
    class LockInput extends Thread {
        LockRes lockRes;
        Condition newCondition;
    
        LockInput(LockRes res, Condition newCondition) {
            this.lockRes = res;
            this.newCondition = newCondition;
        }
    
        @Override
        public void run() {
            while (true) {
                try {
                    //此处，切勿重新new condition,因为生产者和消费者必须要用通一把锁资源，如果重新new的话，则不同了，所以此处需要注意
                    //Condition newCondition=lockRes.lock.newCondition();
                    lockRes.lock.lock();
                    if (!lockRes.flag) {
                        try {
                            newCondition.await();//线程等待
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                    System.out.println(lockRes.userName + "," + lockRes.sex);
                    newCondition.signal();//唤醒
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    lockRes.lock.unlock();
                }
            }
        }
    }
    
    public class LockThread {
        public static void main(String[] args) {
            LockRes res = new LockRes();
            Condition condition = res.lock.newCondition();
            //写的线程
            LockOut out = new LockOut(res, condition);
            //读的线程
            LockInput input = new LockInput(res, condition);
            out.start();
            input.start();
        }
    }

特别注意点是newCondition.await();方法的使用，不能用成是wait方法。

Lock接口与synchroinzed关键字的区别  
    1、Lock接口可以尝试非阻塞的获取锁，当线程尝试获取锁，如果这一时刻锁没有被其他线程获取到，则成功获取并持有锁。  
    2、Lock接口能被中断的获取锁，与synchronized不同，获取到的锁的线程能够响应中断，当获取到的锁的线程被中断时，中断异常将会被抛出，同时锁会被释放。  
    3、Lock接口在指定的截止时间之前获取锁，如果截止时间到了依旧无法获取锁，则返回。