package com.darrenchan.lock;

/**

 * 用两个int变量实现读写锁

 * @author Think

 *

 */

public class MyReadWriteLock {

    private int readcount = 0;

    private int writecount = 0;

    public void lockread() throws InterruptedException{

        while(writecount > 0){

            synchronized(this){

                wait();

            }

        }

        readcount++;

        //进行读取操作

        System.out.println("读操作");

    }

    public void unlockread(){

        readcount--;

        synchronized(this){

            notifyAll();

        }

    }

    public void lockwrite() throws InterruptedException{

        while(writecount > 0){

            synchronized(this){

                wait();

            }

        }

        //之所以在这里先++，是先占一个坑，避免读操作太多，从而产生写的饥饿等待

        writecount++;

        while(readcount > 0){

            synchronized(this){

                wait();

            }

        }

        //进行写入操作

        System.out.println("写操作");

    }

    public void unlockwrite(){

        writecount--;

        synchronized(this){

            notifyAll();

        }

    }

    public static void main(String[] args) throws InterruptedException {

        MyReadWriteLock readWriteLock = new MyReadWriteLock();

        for(int i = 0; i < 2; i++){

            Thread2 thread2 = new Thread2(i, readWriteLock);

            thread2.start();

        }

        for (int i = 0; i < 10; i++) {

            Thread1 thread1 = new Thread1(i, readWriteLock);

            thread1.start();

        }

    }

}

class Thread1 extends Thread{

    public int i;

    public MyReadWriteLock readWriteLock;

    public Thread1(int i, MyReadWriteLock readWriteLock) {

        this.i = i;

        this.readWriteLock = readWriteLock;

    }

    @Override

    public void run() {

        try {

            readWriteLock.lockread();

            Thread.sleep(1000);//模拟耗时

            System.out.println("第"+i+"个读任务");

        } catch (InterruptedException e) {

            e.printStackTrace();

        } finally {

            readWriteLock.unlockread();

        }

    }

}

class Thread2 extends Thread{

    public int i;

    public MyReadWriteLock readWriteLock;

    public Thread2(int i, MyReadWriteLock readWriteLock) {

        this.i = i;

        this.readWriteLock = readWriteLock;

    }

    @Override

    public void run() {

        try {

            readWriteLock.lockwrite();

            Thread.sleep(1000);

            System.out.println("第"+i+"个写任务");

        } catch (InterruptedException e) {

            e.printStackTrace();

        } finally {

            readWriteLock.unlockwrite();

        }

    }

}