创建父类

public class Uncle {

private String name;
private int age;

public Uncle(){

}
public Uncle(String name,int age){

    this.name=name;
    this.age=age;
}

public String getName() {

    return name;
}

public void setName(String name) {

    this.name = name;
}

public int getAge() {

    return age;
}

public void setAge(int age) {

    this.age = age;
}

@Override
public String toString() {

    return "Uncle{" +
            "name='" + name + '\'' +
            ", age=" + age +
            '}';
}
public void fahongbao(){

    System.out.println("舅舅发红包");
}

}

创建子类一：

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");
}

}

创建子类二：

public class UncleTwo extends Uncle{

public void fahongbao(){

    System.out.println("二舅发红包");
}

}

多态子类继承父类

public class Demo {

public static void main(String[] args) {

    UncleOne dajiu=new UncleOne();
    dajiu.fahongbao();
    UncleTwo uncleTwo=new UncleTwo();
    uncleTwo.fahongbao();


    //多态  向上转型
    Uncle dajiu1=new UncleOne();
    dajiu1.fahongbao();
    //子类独有的方在发生向上转型的时候无法在父类中使用

    //dajiu1.songyan(); 会报错
    UncleOne temp=(UncleOne)dajiu1;
    temp.songyan();//可以调用子类独有的方法

    Uncle erjiu=new UncleTwo();
    erjiu.fahongbao();
    //向下转型
    Uncle uncle=new Uncle();
    uncle.fahongbao();

public class Demo01 {

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();
    }
}