向下轉型

class A{
    int a0;
    void funA(){
        System.out.println("funA()");
    }
}

class B extends A {//B繼承A
    int b0;
    void funB(){
        System.out.println("funB()");
    }
}

public class TestDemo{
    public static void main (String args[]){
        A b = new B();//向上轉型為A
        if(b instanceof B){
            B newb = (B)b;//向下轉型為B
        newb.funA();
        newb.funB();
        System.out.println(newb.b0);
        System.out.println(newb.a0);
        }
    }
}