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
UncleTwo uncleTwo = new UncleTwo();
uncleTwo.faHongbao(); // 二舅发红包
```
**向上转型**
```
Uncle dajiu1 = new UncleOne();
dajiu1.faHongbao(); // 大舅发红包
```
**向下转型**
```java
Uncle dajiu1 = new UncleOne();
dajiu1.faHongbao();
//dajiu1.songYan(); // 会报错 子类独有的方法在发生向上转型的时候无法在父类中使用
UncleOne temp = (UncleOne) dajiu1; // 向下转型
temp.songYan(); // 可以调用子类独有的方法
```
# instancesof
