2020.8.17

 1 //父类：
 2 public class CPolygon {
 3     protected int width,height;
 4     public void setValues(int a,int b)
 5     {
 6         width=a;
 7         height=b;
 8     }
 9 }
10 //子类1：长方形
11 public class CRectangle extends CPolygon {
12     public int area() {
13         return width*height;
14     }
15 }
16 //子类2：三角形
17 public class CTriangle extends CPolygon {
18     public int area() {
19         return (width*height)/2;
20     }
21 }
22 //实现类：
23 public class main1 {
24     public static void main(String[] args) {
25         CRectangle rect=new CRectangle();
26         CTriangle trgl=new CTriangle();
27         rect.setValues(4, 5);
28         trgl.setValues(4, 5);
29         System.out.println("长方形面积:"+rect.area());
30         System.out.println("三角形面积:"+trgl.area());
31     }
32 }

 1 //接口1：日期
 2 public interface Date {
 3     public void setDate(int y,int mo,int d);
 4     public void displayDate();
 5 }
 6 //接口2：时间
 7 public interface Time {
 8     public void setTime(int h,int mi,int s);
 9     public void displayTime();
10 }
11 //实现类：
12 public class Datetime implements Date,Time {
13     protected int year,month,day,hour,minute,second;
14     public void setDate(int y,int mo,int d) {
15         year=y;
16         month=mo;
17         day=d;
18     }
19     public void displayDate() {
20         System.out.println(year+"-"+month+"-"+day);
21     }
22     public void setTime(int h,int mi,int s) {
23         hour=h;
24         minute=mi;
25         second=s;
26     }
27     public void displayTime() {
28         System.out.println(hour+":"+minute+":"+second);
29     }
30     public static void main(String[] args) {
31         Datetime dt=new Datetime();
32         dt.setDate(2020, 5, 20);
33         dt.setTime(20, 13,14);
34         dt.displayDate();
35         dt.displayTime();
36     }
37 }