java 多線程生產者消費者

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() + "...生產者..." + this.name);
        flag = true;
        this.notifyAll();
    }

    public synchronized void print() {
        while (flag) {
            System.out.println(Thread.currentThread().getName() + "......消費者......" + 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();

    }
}

出現多個生產者消費者要用while重新判斷一次標記，並使用notifyAll()喚醒所有，notify可能出現只喚醒本方線程的情況，導致所有線程都等待。
缺點：每次都喚醒所有，其實只需要生產者喚醒消費者，消費者喚醒生產者就行了，JDK1.5中就實現了。

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() + "...生產者..." + 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() + "......消費者......" + 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();

    }
}

將synchronized替換成顯示的Lock操作，將Object中的wait，notify，notifyAll替換成了Condition對象，該對象可以通過Lock鎖獲取。

實現了本方只喚醒對方的操作。