Java 多線程實現蜜蜂和熊的問題

蜜蜂和熊的問題

• 100只蜜蜂，2頭熊，每隻蜜蜂每次生產的蜂蜜是1，有一個罐子，容量是50
• 罐子的蜂蜜量一旦到達20，熊就一次喫掉20

注意問題

• 生產和消費函數在等待結束執行完生產消費邏輯後要notifyAll()
• 生產者和消費者執行完生產消費函數後要yield()
• 以上兩點可以保證蜂蜜到達20以後熊儘快開始消費，不然總是等到罐子滿了熊纔開始消費。

代碼

App.java

    public static void main(String[] args) throws Exception {
        HoneyPot pot = new HoneyPot();
        Bear bear1 = new Bear("bear1", pot);
        Bear bear2 = new Bear("bear2", pot);
        bear1.start();
        bear2.start();
        for(int i=1;i<=100;i++){
            new Bee(Integer.toString(i), pot).start();
        }
    }

HoneyPot.java

public class HoneyPot {
    int honey;
    private final static int capacity = 50;

    synchronized void add(int i) throws InterruptedException {
        while (honey == capacity) {
            this.wait();
        }
        honey += i;
        System.out.println("added, pot cp: " + honey);
        this.notifyAll();
    }

    synchronized void remove(int i) throws InterruptedException {
        while (honey < i) {
            this.wait();
        }
        honey -= i;
        System.out.println("removed, pot cp: " + honey);
        this.notifyAll();

    }
}

Bee.java

public class Bee extends Thread {
    private String bname;
    private HoneyPot hp;

    Bee(String bname, HoneyPot hp){
        this.bname = bname;
        this.hp = hp;
    }

    @Override
    public void run() {
        while(true){
            try {
                hp.add(1);
                System.out.println(bname + " : +1");
                this.yield();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

Bear.java

public class Bear extends Thread {
    private String bname;
    private final static int drink = 20;
    private HoneyPot hp;

    Bear(String bname, HoneyPot hp) {
        this.bname = bname;
        this.hp = hp;
    }

    @Override
    public void run() {
        while (true) {
            try {
                hp.remove(drink);
                System.out.println(bname + " - : " + drink);
                this.yield();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}