2021-04-25

笔记

多态

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

    public  Uncle(){

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

子类一

package edu.xcdq;

/**
 * @qvthor liuwenzheng
 * @date 2021/4/25 14:57
 */
public class UncleTwo extends Uncle{
    public void faHongbao(){

        System.out.println("发红包");
    }
    public void songyan(){
        System.out.println("送烟");
    }
}

子类二

package edu.xcdq;

/**
 * @qvthor liuwenzheng
 * @date 2021/4/25 14:56
 */
public class UncleOne extends  Uncle{
    public void faHongbao(){
        System.out.println("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();

向下转型

 Uncle dajiu1 = new UncleOne() ;
       dajiu1.fahongbao();
       //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
        //dajiu1.songyan     //会报错
        UncleOne temp = (UncleOne) dajiu1 ; //向下转型
        temp.songyan(); //可以调用子类独有的方法

instanceof

判断对象是否是指定的类型实例

避免发生错误的类型转换

package edu.xcdq;

/**
 * @qvthor liuwenzheng
 * @date 2021/4/25 15:58
 */
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();
        }
    }
}

Demo01

package edu.xcdq;

/**
 * @qvthor liuwenzheng
 * @date 2021/4/25 14:45
 */
public class Demo01 {
    public static void main(String[] args) {
        //多态
       UncleOne dajiu = new UncleOne();
       dajiu.faHongbao();
       UncleTwo uncleTwo = new UncleTwo() ;
       uncleTwo.faHongbao();

       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 ;
        temp.songyan();

       Uncle erjiu = new UncleTwo() ;
       erjiu.fahongbao();

       //向下转型
        Uncle uncleTwo1 = new UncleTwo() ;
        UncleTwo temp1 = (UncleTwo) uncleTwo;
        temp.faHongbao();
    }

}

Demo02

package edu.xcdq;

/**
 * @qvthor liuwenzheng
 * @date 2021/4/25 15:58
 */
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();
        }
    }
}

Uncle

package edu.xcdq;

/**
 * @qvthor liuwenzheng
 * @date 2021/4/25 14:47
 */
public class Uncle {
    private  String name ;
    private  int age ;

    public  Uncle(){

    }
    public  Uncle(String name , int age){
        this.name = name ;
        this.age = age ;
    }
    public void fahongbao(){
        System.out.println("发红包");
    }

    public String getName(){
        return  name ;
    }

    @Override
    public String toString() {
        return "Uncle{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    public int getAge() {
        return age;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setAge(int age) {
        this.age = age;
    }

}

UncleOne

package edu.xcdq;

/**
 * @qvthor liuwenzheng
 * @date 2021/4/25 14:56
 */
public class UncleOne extends  Uncle{
    public void faHongbao(){
        System.out.println("发红包");
    }
    public void songyan(){
        System.out.println("送烟");
    }
}

UncleTwo

package edu.xcdq;

/**
 * @qvthor liuwenzheng
 * @date 2021/4/25 14:57
 */
public class UncleTwo extends Uncle{
    public void faHongbao(){
        System.out.println("发红包");
    }

}