⑤ 生产消费者模式

这个模式是我们最熟悉的模式了，一边可劲的造，一边可劲的吃。

那么这个模式的核心是什么呢？我按从左往右放，你从右往左拿。莫要乱了顺序。就不能从左往右拿吗？其实也是可以的，哈哈，怎么拿都随你，但是不同方法的算法不同罢了。无所谓。

关键点就是满了就不能放了，空了就不能拿了。

我们明确一个条件：先进先出，就是先创建的先消费，以免放坏，我们用不同的符号来表示拿的和放的位置。

情景：幼儿园老师现场给小朋友们做蛋糕，烤好一个就往桌子的盘子里放一个，假设桌子总共可以放 5 个。小朋友5个，做面包的老师2个。老师大概2分钟做一个，小朋友大概3、5分钟吃一个.

首先我们需要创建这个神奇的桌子。

老师放蛋糕的时候，就不要考虑小朋友拿到了哪一个，只考虑，桌子上是否放满了，放满就等待，没放满就接着放，纯粹一点不是更简单吗。

小朋友拿蛋糕的也是纯粹一些，就看桌子上是否有蛋糕，有就拿，没有就等待。

public class Table {
    private int count;//蛋糕的总数
    //拿蛋糕  和 放蛋糕 就按顺序来  1 2 3
    String[] buffer;
    private int tail;//下次 放 的位置
    private int head;//下次 拿 的位置
    public Table(int count) {
        this.buffer = new String[count];
        this.count = count;
        this.tail = 0;
        this.head = 0;
        this.count = 0;
    }
    public synchronized void put(String take) throws InterruptedException {
        try {
            while (count >= buffer.length) {
                wait();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        buffer[tail] = take;
        tail = (tail + 1) % buffer.length;
        count++;
        notifyAll();
        System.out.println(Thread.currentThread().getName() + "  put()  " + take);
    }
    public synchronized String take() throws InterruptedException {
        try {
            while (count <= 0) {
                wait();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        String take = buffer[head];
        head = (head + 1) % buffer.length;
        count--;
        notifyAll();
        System.out.println(Thread.currentThread().getName() + "  take()  " + take);
        return take;
    }
}

public class MakerThread extends Thread {
    private final Table table;
    private static int number = 0;
    public MakerThread(String name, Table table) {
        super(name);
        this.table = table;
    }
    @Override
    public void run() {
        super.run();
        while (true) {
            try {
                Thread.sleep(2000);
                table.put(number++ + "");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

public class EaterThread extends Thread {
    private final Table table;
    public EaterThread(String name, Table table) {
        super(name);
        this.table = table;
    }
    @Override
    public void run() {
        super.run();
            while (true) {
                try {
                    Thread.sleep(5000);
                    table.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
    }
}

public class Main {
    public static void main(String[] args) {
        Table table = new Table(5);
        MakerThread makerThread1 = new MakerThread("MakerThread1", table);
        MakerThread makerThread2 = new MakerThread("MakerThread2", table);
        makerThread1.start();
        makerThread2.start();
        EaterThread eaterThread1 = new EaterThread("EaterThread1", table);
        EaterThread eaterThread2 = new EaterThread("EaterThread2", table);
        EaterThread eaterThread3 = new EaterThread("EaterThread3", table);
        EaterThread eaterThread4 = new EaterThread("EaterThread4", table);
        EaterThread eaterThread5 = new EaterThread("EaterThread5", table);
        eaterThread1.start();
        eaterThread2.start();
        eaterThread3.start();
        eaterThread4.start();
        eaterThread5.start();
    }
}