手动实现一个可重入锁

Posted 2020-10-19 凌晨六点半

package com.roocon.thread.ta1;

public class Sequence {

    private MyLock lock = new MyLock();

    private int value;

    public int getNext() {
        lock.lock();
        value++;
        lock.unlock();
        return value;

    }

    public static void main(String[] args) {

        Sequence s = new Sequence();

        new Thread(new Runnable() {

            @Override
            public void run() {
                while(true)
                    System.out.println(s.getNext());
            }
        }).start();
        new Thread(new Runnable() {

            @Override
            public void run() {
                while(true)
                    System.out.println(s.getNext());
            }
        }).start();
        new Thread(new Runnable() {

            @Override
            public void run() {
                while(true)
                    System.out.println(s.getNext());
            }
        }).start();
        new Thread(new Runnable() {

            @Override
            public void run() {
                while(true)
                    System.out.println(s.getNext());
            }
        }).start();
        new Thread(new Runnable() {

            @Override
            public void run() {
                while(true)
                    System.out.println(s.getNext());
            }
        }).start();
    }

}

 

package com.roocon.thread.ta1;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

public class MyLock implements Lock {

    private boolean isLocked = false;

    @Override
    public synchronized void lock() {
        /*
         if (isLocked == false) {//第一个进来的线程不需要等待
            isLocked = true;
        }else {//其他线程需要等待
            try {
                wait();//使用wait模拟等待
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
         */
        if (isLocked) {
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        isLocked = true;

    }

    @Override
    public synchronized void unlock() {
        isLocked = false;
        notify();//wait notify 必须和synchronized一起使用
    }


    @Override
    public void lockInterruptibly() throws InterruptedException {

    }

    @Override
    public boolean tryLock() {
        return false;
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return false;
    }

    @Override
    public Condition newCondition() {
        return null;
    }
}

 

运行结果：

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