一個java文件中可以包含多個類，但這些類中一個特殊類，這個類的屬性為public，且這個類的名字與文件名相同，java文件中僅有一個類為public.

 interface Moveable {
    void run();
}

//具體產品角色
 class Plane implements Moveable {
    @Override
    public void run() {
        System.out.println("plane....");
    }
}

 class Broom implements Moveable {
    @Override
    
 
public void run() {
        System.out.println("broom.....");
    }
}

//抽象工廠
abstract class VehicleFactory {
    abstract Moveable create();
}
//具體工廠
 class PlaneFactory extends VehicleFactory{
    public Moveable create() {
        return new Plane();
    }
}
 class BroomFactory extends VehicleFactory{
    
 
public Moveable create() {
        return new Broom();
    }
}
//測試類
public class Main {
    public static void main(String[] args) {
        VehicleFactory factory = new BroomFactory();
        Moveable m = factory.create();
        m.run();
    }
}

java 一個文件中寫多個class