// 抽象父类Vehicle
abstract class Vehicle {
    // 抽象方法run()
    public abstract void run();
}

// 子类Car
class Car extends Vehicle {
    public void run() {
        System.out.println("Car is running");
    }
}

// 子类Bike
class Bike extends Vehicle {
    public void run() {
        System.out.println("Bike is running");
    }
}

// 子类Truck
class Truck extends Vehicle {
    public void run() {
        System.out.println("Truck is running");
    }
}

// 测试类
class VehicleTest {
    public static void main(String[] args) {
        // 创建Vehicle数组
        Vehicle[] vehicles = new Vehicle[3];
        vehicles[0] = new Car();
        vehicles[1] = new Bike();
        vehicles[2] = new Truck();
        
        // 遍历调用run()方法
        for (Vehicle vehicle : vehicles) {
            vehicle.run();
        }
    }
}