用java创建一个名为Vehicle的抽象类，具有一个名为start()的抽象方法和一个名为stop()的具体方法。创建两个子类Car和Motorcycle，并实现它们的start()方法。在Main类中创建一个Vehicle数组并用各种不同类型的Vehicle对象填充它，然后循环遍历该数组并分别调用每个Vehicle对象的start()和stop()方法。

好的，以下是Java代码实现：

public abstract class Vehicle {
    public abstract void start();
    public void stop() {
        System.out.println("Vehicle stopped.");
    }
}

public class Car extends Vehicle {
    @Override
    public void start() {
        System.out.println("Car started.");
    }
}

public class Motorcycle extends Vehicle {
    @Override
    public void start() {
        System.out.println("Motorcycle started.");
    }
}

public class Main {
    public static void main(String[] args) {
        Vehicle[] vehicles = new Vehicle[3];
        vehicles[0] = new Car();
        vehicles[1] = new Motorcycle();
        vehicles[2] = new Car();
        
        for(Vehicle vehicle: vehicles) {
            vehicle.start();
            vehicle.stop();
        }
    }
}

运行结果如下：

Car started.
Vehicle stopped.
Motorcycle started.
Vehicle stopped.
Car started.
Vehicle stopped.