多态
父类
public class Uncle {
private String name;
private int age
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("大舅发红包");
}
public void songYan(){
System.out.println("大舅喜欢送烟");
}
}
子类二
public class UncleTwo extends Uncle{
public void fahongbao(){
System.out.println("二舅发红包");
}
}
多态
UncleOne dajiu = new UncleOne();
dajiu.fahongbao();// 大舅发红包
Uncle erjiu = new Uncle();
erjiu.fahongbao(); // 二舅发红包
向上转型
Uncle dajiu1 = new Uncle();
dajiu1.fahongbao();
向下转型
Uncle dajiu1 = new Uncle();
dajiu1.fahongbao();
// 子类独有的方法会无法在父类中使用
//dajiu1.songYan(); // 会报错
UncleOne d = (UncleOne) dajiu1;
d.songYan();
instanceof
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 Demo2 {
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();
}
}
}
