多态

父类

public class Uncle {
    private String name;
    private int age;
public void fahongbao(){
    System.out.println("大舅发红包");
   }
}

子类一：

        System.out.println("大舅发红包");
    }
    public void songyan(){
        System.out.println("大舅喜欢送烟");
    }
}

子类二：

        public void fahongbao(){
            System.out.println("二舅发红包");
        }
    }

多态

UncleOne dajiu = new UncleOne();
dajiu.fahongbao();  //大舅发红包
UncleTwo uncleTwo = new UncleTwo();
uncleTwo.getName(); //二舅发红包

向上转型

UncleOne dajiu1 = new UncleOne();
dajiu1.fahongbao();  //大舅发红包

向下转型

UncleOne dajiu1 = new UncleOne();
dajiu1.fahongbao();
 // dajiu1.songyan();  // 会报错 子类独有的方法会无法再父类中使用
    UncleOne temp = (UncleOne) dajiu1；  //向下转型
        temp.songyan(); //可以调用子的方法

instancesof

判断对象是否是指定的类型的实例

避免发生错误的类型转换

public class Demo02 {
    public static void main(String[] args) {
        Uncle uncle1 = new UncleOne();
        Uncle uncle2 = new UncleTwo();
        if(uncle1 instanceof UncleOne){
            UncleOne u1 = (UncleOne)uncle1;
            u1.fahongbao();
        }
        if(uncle2 instanceof UncleTwo) {
            UncleTwo u2 = (UncleTwo) uncle2;
            u2.fahongbao();
        }
    }