java——作业2

一、

1.B 成员变量不能直接操作

2.C x不是类成员

3.D double 转 int 数据会损失

二、

1. 100:20

2. 21:21

三、

public class 作业
{
    public static void main(String arags[])
    {
        CPU cpu = new CPU();
        cpu.setSpeed(2200);

        HardDisk disk = new HardDisk();
        disk.setAmount(200);

        PC pc = new PC();
        pc.setCpu(cpu);
        pc.setHD(disk);
        pc.show();
    }

}

class CPU
{
    int speed;
    public void setSpeed(int temp)
    {
        this.speed=temp;
    }
    public int getSpeed()
    {
        return this.speed;
    }
}

class HardDisk
{
    int amount;
    void setAmount(int temp)
    {
        this.amount=temp;
    }
    int getAmount()
    {
        return this.amount;
    }
}

class PC
{
    CPU cpu;
    HardDisk HD;
    void setCpu(CPU temp)
    {
        this.cpu=temp;
    }
    void setHD(HardDisk temp)
    {
        this.HD=temp;
    }
    void show()
    {
        System.out.println("PC speed is "+cpu.getSpeed()+" and amount is "+HD.getAmount());
    }
}

public class work
{
    public static void main(String [] a)
    {
        Simulator simulator=new Simulator();
        simulator.playSound(new Dog());
        simulator.playSound(new Cat());
    }
}

abstract class Animal
{
    abstract public void cry();
    abstract public void getAnimalName();
}

class Dog extends Animal
{
    @Override
    public void cry()
    {
        System.out.println("汪汪");
    }
    @Override
    public void getAnimalName()
    {
        System.out.println("我不是人，你是真狗");
    }

}

class Cat extends Animal
{
    @Override
    public void cry()
    {
        System.out.println("喵了个咪");
    }
    @Override
    public void getAnimalName()
    {
        System.out.println("我是猫");
    }

}

class Simulator
{
    public void playSound(Animal animal)
    {
        animal.cry();
        animal.getAnimalName();
    }
}