编写一个Java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。 (1)每个类都有构造方法进行属性初始化; (2)每个类都输出相关数据信息的成员方法; (3)使用Test类中的main方法实例化各类，并输出相关信息。

下面是Java程序的实现：

class Vehicle {
    private int wheels;
    private double weight;

    public Vehicle(int wheels, double weight) {
        this.wheels = wheels;
        this.weight = weight;
    }

    public int getWheels() {
        return wheels;
    }

    public double getWeight() {
        return weight;
    }

    public void printInfo() {
        System.out.println("Wheels: " + wheels + ", Weight: " + weight);
    }
}

class Car extends Vehicle {
    private int loader;

    public Car(int wheels, double weight, int loader) {
        super(wheels, weight);
        this.loader = loader;
    }

    public int getLoader() {
        return loader;
    }

    public void printInfo() {
        super.printInfo();
        System.out.println("Loader: " + loader);
    }
}

class Truck extends Car {
    private double payload;

    public Truck(int wheels, double weight, int loader, double payload) {
        super(wheels, weight, loader);
        this.payload = payload;
    }

    public double getPayload() {
        return payload;
    }

    public void printInfo() {
        super.printInfo();
        System.out.println("Payload: " + payload);
    }
}

public class Test {
    public static void main(String[] args) {
        Vehicle v = new Vehicle(4, 1000.0);
        Car c = new Car(4, 1200.0, 5);
        Truck t = new Truck(6, 5000.0, 2, 10000.0);

        v.printInfo();
        c.printInfo();
        t.printInfo();
    }
}

在Test类中，我们实例化了一个Vehicle对象v、一个Car对象c和一个Truck对象t，并分别调用它们的printInfo方法输出相关信息。其中，Car和Truck类继承了Vehicle类的属性和方法，并增加了自己的属性和方法。在输出信息时，我们先调用父类的printInfo方法，再输出自己的属性信息。