review36

Posted 2020-12-30 liaoxiaolao

对于Thread(Runnable target)构造方法创建的线程，轮到它来享用CPU资源时，目标对象就会自动调用接口中的run()方法，因此，对于使用同一目标对象的线程，目标对象的成员变量自然就是线程共享的数据单元。

下面的例子中，房屋就是线程的目标对象，房屋中的一桶水被猫和狗共享。

public class Test07 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        House house = new House();
        house.setWater(10);
        Thread dog, cat;
        dog = new Thread(house);
        cat = new Thread(house);
        dog.setName("狗");
        cat.setName("猫");
        dog.start();
        cat.start();
    }

}

House.java

public class House implements Runnable {
    int waterAmount;
    public void setWater(int w)
    {
        waterAmount = w;
    }

    @Override
    public void run() {
        // TODO Auto-generated method stub
        while(true)
        {
            String name = Thread.currentThread().getName();
            if(name.equals("狗"))
            {
                System.out.println(name + "喝水");
                waterAmount = waterAmount -2;
            }
            else if(name.equals("猫"))
            {
                System.out.println(name + "喝水");
                waterAmount = waterAmount - 1;
            }
            System.out.println(" 剩 " + waterAmount);
            try{
                Thread.sleep(2000);
            }
            catch(InterruptedException e){}
            if(waterAmount <= 0)
            {
                return;
            }
        }
    }

}

运行结果如下所示：

 

目标对象可以组合线程，即将线程作为自己的成员（弱耦合）。

可以这样改

public class Test01 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        House house = new House();
        house.setWater(10);
        house.dog.start();
        house.cat.start();
    }

}

House.java

public class House implements Runnable {

    int waterAmount;
    Thread dog, cat;
    House()
    {
        dog = new Thread(this);
        cat = new Thread(this);
    }
    public void setWater(int water)
    {
        waterAmount = water;
    }
    @Override
    public void run() {
        // TODO Auto-generated method stub
        while(true)
        {
            Thread thread = Thread.currentThread();
            if(thread == dog)
            {
                System.out.println("家狗喝水 -2");
                waterAmount = waterAmount - 2;
            }
            else if(thread == cat)
            {
                System.out.println("家猫喝水 -1");
                waterAmount = waterAmount - 1;
            }
            try{
                Thread.sleep(2000);
            }
            catch(InterruptedException e){}
            if(waterAmount <= 0)
            {
                return;
            }
        }
    }

}

 运行结果如下所示：