編寫一個Java應用程序，設計一個汽車類Vehicle，包含的屬性有車輪個數 wheels和車重weight。小車類Car是Vehicle的子類，其中包含的屬性有載人數 loader。卡車類Truck是Car類的子類，其中包含的屬性有載重量payload。每個 類都有構造方法和輸出相關數據的方法。最后，寫一個測試類來測試這些類的功 能。

package car;

public class Vehicle
{
    //定義成員變量
    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;
    }    
        
    //構造方法
    public Vehicle(int wheels, double weight) {
        super();
        this.wheels = wheels;
        this.weight = weight;
    }
    
    
    
}

package car;

public class Car extends Vehicle {
    // 定義新的成員變量
    private int loader;

    public int getLoader() {
        return loader;
    }

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

    // 調用父類構造方法
    public Car(int wheels, double weight,int loader) {
        super(wheels, weight);
        this.loader=loader;
        
    }
}

package car;

public class Truck extends Car
{ 
    //添加新的成員變量
    private double payload;

    public double getPayload() {
        return payload;
    }

    public void setPayload(double payload) {
        this.payload = payload;
    }
    
    //調用父類構造方法
    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) {

        //實例化Vehicle對象
        Vehicle v= new Vehicle(4,2);
        System.out.println("汽車A有"+v.getWheels()+"個輪子,它的重量是"+v.getWeight()+"噸");
        
        
        //實例化car對象
        Car c = new Car(8,2,20);
        System.out.println("汽車B有"+c.getWheels()+"個輪子,它的重量是"+c.getWeight()+"噸,能載"+c.getLoader()+"個人");
        
        
        //實例化Truck對象
        Truck t= new Truck(8,3,4,10);
        System.out.println("汽車C有"+t.getWheels()+"個輪子,它的重量是"+t.getWeight()+"噸,能載"+t.getLoader()+"個人,能裝"+t.getPayload()+"噸貨");
    }

}