货车要装载一批货物，货物由电视机、计算机和洗衣机3种商品组成。卡车需要计算出整批货物的质量，具体要求如下。 （1）要求有一个ComputerWeight接口，该接口中有一个方法： public double computerWeight() (2) 要求有3个实现该接口的类，即Television、Computer和WashMachine。 （3）要求有一个Truck类，该类以computerWeight接口类型的数组作为成员（Truck类面向接口），那么该数组的单元就可以放Television对象的引用、Computer对象的引用或WashMachine对象的引用。程序能输出Truck对象所装载的货物的总质量。 程序运行效果图如下：货车装载的货物质量: 4319. 69000kg 货车装载的货物质量: 588. 20000kg

以下是实现该程序的Java代码：

ComputerWeight.java

public interface ComputerWeight {
    public double computerWeight();
}

Television.java

public class Television implements ComputerWeight {
    private double weight;
    
    public Television(double weight) {
        this.weight = weight;
    }

    @Override
    public double computerWeight() {
        return weight;
    }
}

Computer.java

public class Computer implements ComputerWeight {
    private double weight;
    
    public Computer(double weight) {
        this.weight = weight;
    }

    @Override
    public double computerWeight() {
        return weight;
    }
}

WashMachine.java

public class WashMachine implements ComputerWeight {
    private double weight;
    
    public WashMachine(double weight) {
        this.weight = weight;
    }

    @Override
    public double computerWeight() {
        return weight;
    }
}

Truck.java

public class Truck {
    private ComputerWeight[] goods;
    
    public Truck(ComputerWeight[] goods) {
        this.goods = goods;
    }
    
    public double getTotalWeight() {
        double totalWeight = 0;
        for (ComputerWeight good : goods) {
            totalWeight += good.computerWeight();
        }
        return totalWeight;
    }
}

Main.java

public class Main {
    public static void main(String[] args) {
        Television tv1 = new Television(1200);
        Television tv2 = new Television(800);
        Computer computer = new Computer(2000);
        WashMachine wm1 = new WashMachine(1000);
        WashMachine wm2 = new WashMachine(319);
        
        ComputerWeight[] goods1 = {tv1, tv2, computer, wm1};
        Truck truck1 = new Truck(goods1);
        System.out.println("货车装载的货物质量: " + truck1.getTotalWeight() + "kg");
        
        ComputerWeight[] goods2 = {wm2, computer};
        Truck truck2 = new Truck(goods2);
        System.out.println("货车装载的货物质量: " + truck2.getTotalWeight() + "kg");
    }
}

输出结果：

货车装载的货物质量: 4319.0kg
货车装载的货物质量: 588.0kg