java 多线程生产者消费者 Lock对象

 

class Res {    private String name;    private int count = 1;    private boolean flag;    public synchronized void set(String name) {        while (flag) {            try {                this.wait();            } catch (InterruptedException e) {                e.printStackTrace();            }        }        this.name = name + "--" + count++;        System.out.println(Thread.currentThread().getName() + "...生产者..." + this.name);        flag = true;        this.notifyAll();    }    public synchronized void print() {        while (flag) {            System.out.println(Thread.currentThread().getName() + "......消费者......" + this.name);            flag = false;            this.notifyAll();        }    }}class Producer implements Runnable {    private Res r;    public Producer(Res r) {        this.r = r;    }    @Override    public void run() {        while (true) {            r.set("商品");        }    }}class Consumer implements Runnable {    private Res r;    public Consumer(Res r) {        this.r = r;    }    @Override    public void run() {        while (true) {            r.print();        }    }}public class ProducerConsumerDemo {    public static void main(String[] args) {        Res r = new Res();        new Thread(new Producer(r)).start();        new Thread(new Producer(r)).start();        new Thread(new Consumer(r)).start();        new Thread(new Consumer(r)).start();    }}

出现多个生产者消费者要用while重新判断一次标记，并使用notifyAll()唤醒所有，notify可能出现只唤醒本方线程的情况，导致所有线程都等待。
缺点：每次都唤醒所有，其实只需要生产者唤醒消费者，消费者唤醒生产者就行了，JDK1.5中就实现了。

import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;class Res {    private String name;    private int count = 1;    private boolean flag;    private Lock lock = new ReentrantLock();    private Condition condition__pro = lock.newCondition();    private Condition condition__con = lock.newCondition();    public void set(String name) throws InterruptedException {        lock.lock();        try {            while (flag) condition__pro.await();            this.name = name + "--" + count++;            System.out.println(Thread.currentThread().getName() + "...生产者..." + this.name);            flag = true;            condition__con.signal();        } finally {            lock.unlock();        }    }    public void print() throws InterruptedException {        lock.lock();        try {            while (!flag)                condition__con.await();                System.out.println(Thread.currentThread().getName() + "......消费者......" + this.name);                flag = false;                condition__pro.signal();        }finally {            lock.unlock();        }    }}class Producer implements Runnable {    private Res r;    public Producer(Res r) {        this.r = r;    }    @Override    public void run() {        while (true) {            try {                r.set("商品");            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }}class Consumer implements Runnable {    private Res r;    public Consumer(Res r) {        this.r = r;    }    @Override    public void run() {        while (true) {            try {                r.print();            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }}public class ProducerConsumerDemo {    public static void main(String[] args) {        Res r = new Res();        new Thread(new Producer(r)).start();        new Thread(new Producer(r)).start();        new Thread(new Consumer(r)).start();        new Thread(new Consumer(r)).start();    }}

将synchronized替换成显示的Lock操作，将Object中的wait，notify，notifyAll替换成了Condition对象，该对象可以通过Lock锁获取。

实现了本方只唤醒对方的操作。