多态

多态

父类

public class Uncle {
    private  String name;
    private  int  aeg;

    public  void faHongbao(){
        System.out.println("舅舅发红包");
    }

}

子类一：

public class UncleOne extends Uncle {
    public void faHongbao() {
        System.out.println("大舅不仅发红包，还送烟");

    }
        public void chouyan () {
            System.out.println("大舅喜欢抽烟");

        }
    }

子类二：

public class UncleTow extends Uncle{
    public void faHongbao() {
        System.out.println("二舅发红包");
    }
}

多态

 public static void main(String[] args) {
        // 多态
        Uncle uncle1 = new UncleOne();
        uncle1.faHongbao();
        Uncle uncle2 = new UncleTow(); // // 向上转型
        uncle2.faHongbao();

多父类名接受子类创建的对象，只能调用父类出现过的方法,子类的扩展的独有方法无法调用

public static void main(String[] args) {
        // 多态
        Uncle uncle1 = new UncleOne();
        uncle1.faHongbao();
        //uncle1.chouyan(); 不能调用

向上转型

 Uncle uncle2 = new UncleTow(); // // 向上转型
        uncle2.faHongbao();

向下转型

Uncle uncle =new uncleOne;
UncleOne u1 = (UncleOne) uncle1;// 向下转
        u1.faHongbao();
        u1.chouyan();

instanceof

判断对象是否给定的类的实例

作用：避免类型转换时，出现错误，进而引发程序的崩溃
public class Demo01 {
public static void main(String[] args) {
Uncle uncle1 = new UncleOne();
if (uncle1 instanceof UncleTow) {
UncleTow u2 = (UncleTow) uncle1;
u2.faHongbao();
}
if ( uncle1 instanceof UncleOne){
UncleOne u1 = (UncleOne) uncle1;
u1.faHongbao();
u1.chouyan();
}
}
}