Java 多线程基础（十二）生产者与消费者

public class Bread {
    private int capacity;    // 面包的容量
    private int size;        // 面包的实际数量
    public Bread(int capacity) {
        this.capacity = capacity;
        this.size = 0;
    }
    
    // 生产面包
    public synchronized void produce(int val) {
        try {
             // left 表示“想要生产的数量”(有可能生产量太多，需多此生产)
            int left = val;
            while (left > 0) {
                // 库存已满时，等待“消费者”消费产品。
                while (size >= capacity)
                    wait();
                // 获取“实际生产的数量”(即库存中新增的数量)
                // 如果“库存”+“想要生产的数量”>“总的容量”，则“实际增量”=“总的容量”-“当前容量”。(此时填满仓库)
                // 否则“实际增量”=“想要生产的数量”
                int inc = (size+left)>capacity ? (capacity-size) : left;
                size += inc;
                left -= inc;
                System.out.printf("%s produce(%3d) --> left=%3d, inc=%3d, size=%3d\n",
                        Thread.currentThread().getName(), val, left, inc, size);
                // 通知“消费者”可以消费了。
                notifyAll();
            }
        }catch(InterruptedException e) {
            e.printStackTrace();
        }
    }
    // 消费面包
    public synchronized void consume(int val) {
        try {
             // left 表示“客户要消费数量”(有可能消费量太大，库存不够，需多此消费)
            int left = val;
            while (left > 0) {
                // 库存为0时，等待“生产者”生产产品。
                while (size )
                    wait();
                // 获取“实际消费的数量”(即库存中实际减少的数量)
                // 如果“库存”// 否则，“实际消费量”=“客户要消费的数量”。
                int dec = (size size : left;
                size -= dec;
                left -= dec;
                System.out.printf("%s consume(%3d) ,
                        Thread.currentThread().getName(), val, left, dec, size);
                notifyAll();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

public class Producer{
    Bread bread;
    public Producer(Bread bread) {
        this.bread = bread;
    }
    public void produce(final int val) {
        new Thread(() -> {
            bread.produce(val);
        }).start();;
    }
}

public class Customer {
    private Bread bread;
    public Customer(Bread bread) {
        this.bread = bread;
    }
    public void consume(final int val) {
        new Thread(() -> {
            bread.consume(val);
        }).start();;
    }
}

public class Demo {
    public static void main(String[] args) {
        Bread bread = new Bread(100);
        Producer producer = new Producer(bread);
        Cunstomer customer = new Customer(bread);
        
        producer.produce(60);
        producer.produce(120);
        consumer.consume(90);
        consumer.consume(150);
        producer.produce(110);
    }
}

// 运行结果
Thread-1 produce( 60) --> left=  0, inc= 60, size= 60
Thread-5 produce(110) --> left= 70, inc= 40, size=100
Thread-4 consume(150) 
Thread-2 produce(120) --> left= 20, inc=100, size=100
Thread-3 consume( 90) 
Thread-4 consume(150) 
Thread-5 produce(110) --> left=  0, inc= 70, size= 70
Thread-4 consume(150) 
Thread-2 produce(120) --> left=  0, inc= 20, size= 50