编写一个Java应用程序，设计一个汽车类Vehicle，包含的属性有车轮个数 wheels和车重weight。小车类Car是Vehicle的子类，其中包含的属性有载人数 loader。卡车类Truck是Car类的子类，其中包含的属性有载重量payload。每个 类都有构造方法和输出相关数据的方法。最后，写一个测试类来测试这些类的功 能。

package car;

public class Vehicle
{
    //定义成员变量
    private int wheels;
    private double weight;
    public int getWheels() {
        return wheels;
    }
    public void setWheels(int wheels) {
        this.wheels = wheels;
    }
    public double getWeight() {
        return weight;
    }
    public void setWeight(double weight) {
        this.weight = weight;
    }    

    //构造方法
    public Vehicle(int wheels, double weight) {
        super();
        this.wheels = wheels;
        this.weight = weight;
    }

}

package car;

public class Car extends Vehicle {
    // 定义新的成员变量
    private int loader;

    public int getLoader() {
        return loader;
    }

    public void setLoader(int loader) {
        this.loader = loader;
    }

    // 调用父类构造方法
    public Car(int wheels, double weight,int loader) {
        super(wheels, weight);
        this.loader=loader;

    }
}

package car;

public class Truck extends Car
{
    //添加新的成员变量
    private double payload;

    public double getPayload() {
        return payload;
    }

    public void setPayload(double payload) {
        this.payload = payload;
    }

    //调用父类构造方法
    public Truck(int wheels, double weight, int loader, double payload ) {
        super(wheels, weight, loader);
        this.payload=payload;
    }

}

package car;

public class Text_car {

    public static void main(String[] args) {

        //实例化Vehicle对象
        Vehicle v= new Vehicle(4,2);
        System.out.println("汽车A有"+v.getWheels()+"个轮子,它的重量是"+v.getWeight()+"吨");

        //实例化car对象
        Car c = new Car(8,2,20);
        System.out.println("汽车B有"+c.getWheels()+"个轮子,它的重量是"+c.getWeight()+"吨,能载"+c.getLoader()+"个人");

        //实例化Truck对象
        Truck t= new Truck(8,3,4,10);
        System.out.println("汽车C有"+t.getWheels()+"个轮子,它的重量是"+t.getWeight()+"吨,能载"+t.getLoader()+"个人,能装"+t.getPayload()+"吨货");
    }

}