这道题用到的知识点：卡车要装载一批货物，货物有3种商品：电视、冰箱和洗衣机。需要计算出大货车和小货车各自所装载的3种货物的总重量。编写一个Java应用程序：（1）要求有一个ComputeWeight接口，该接口中有一个方法：public double computeWeight(); （2）有3个实现该接口的类：Television、Refrigerator和WashMachine。这3个类通过实现接口ComputeWeight给出自重。 （3）有一个Truck类，该类用ComputeWeight接口类型的数组作为成员，那么该数组的元素就可以存放Television对象的引用、Refrigerator对象的引用或WashMachine对象的引用。 （4）程序能输出Truck对象所装载的货物的总重量。

这道题主要考察Java中的接口和类的使用，下面是代码实现：

1. ComputeWeight接口：

public interface ComputeWeight {
    public double computeWeight();
}

2. Television、Refrigerator和WashMachine类的实现：

public class Television implements ComputeWeight {
    private double weight = 10.0; // 电视的自重为10.0kg
    public double computeWeight() {
        return weight;
    }
}

public class Refrigerator implements ComputeWeight {
    private double weight = 50.0; // 冰箱的自重为50.0kg
    public double computeWeight() {
        return weight;
    }
}

public class WashMachine implements ComputeWeight {
    private double weight = 30.0; // 洗衣机的自重为30.0kg
    public double computeWeight() {
        return weight;
    }
}

3. Truck类：

public class Truck {
    private ComputeWeight[] goods;

    public Truck(ComputeWeight[] goods) {
        this.goods = goods;
    }

    public double getTotalWeight() {
        double totalWeight = 0.0;
        for (int i = 0; i < goods.length; i++) {
            totalWeight += goods[i].computeWeight();
        }
        return totalWeight;
    }
}

4. 调用Truck类获取货物总重量：

public class Main {
    public static void main(String[] args) {
        ComputeWeight[] goods = new ComputeWeight[5];
        goods[0] = new Television();
        goods[1] = new Refrigerator();
        goods[2] = new WashMachine();
        goods[3] = new Television();
        goods[4] = new WashMachine();

        Truck truck = new Truck(goods);
        System.out.println("Truck total weight: " + truck.getTotalWeight() + "kg");
    }
}

输出结果：

Truck total weight: 130.0kg