父类

1 package hello; 2  3 public class Yinshuiji {
   //创建父类饮水机 4      5      6     public Yinshuiji(String pinpai,int shuiliang){
   //构造方法 7          8         this.pinpai = pinpai;//品牌 9         this.shuiliang = shuiliang;//当前水量10         System.out.println("饮水机品牌是：" +pinpai + ", 当前水量为" +shuiliang );11         12     }13     14     String pinpai;15     int shuiliang;16     int shengyushuiliang;17     18     //方法一：接水19     public void jieshui(int jieshuiliang){20         21         if(jieshuiliang > shuiliang){22             System.out.println("已经没水了");23         }24         else25         {26             shengyushuiliang = shuiliang - jieshuiliang;27             System.out.println("饮水机剩余水量 = " + shengyushuiliang);28         }29             30     }31     32     //方法二：烧水33     public void shaoshui(int time){34         35         int shuiwen = 20;36         shuiwen = shuiwen + time * 10;37         if(shuiwen > 100)38         {39             System.out.println("水已经开了");40         }41         else42         {43             System.out.println("现在水温 = " + shuiwen);44         }45         46     }47     48 49 }

子类

package hello;public class Dagonglvysj extends Yinshuiji {
   //创建子类大功率饮水机    public Dagonglvysj(String pinpai, int shuiliang) {        super(pinpai, shuiliang);        // TODO Auto-generated constructor stub    }        //重写父类方法二    public void shaoshui(int time)        {        int shuiwen = 20;        shuiwen = shuiwen + time * 20;        if(shuiwen > 100)        {            System.out.println("水已经开了");        }        else        {            System.out.println("现在水温 = " + shuiwen);        }            }}

向上转型

package hello;public class Test {    public static void main(String[] args){                Yinshuiji ysj = new Dagonglvysj("美帝",50);//向上转型                ysj.shaoshui(2);//调用子类重写的方法二