java_第4章 继承与多态_第4周编程题_将MP3媒体类型存放进Database

 1 import java.util.ArrayList;
 2 
 3 public class Database {
 4     private ArrayList<Item> listItem = new ArrayList<Item>();//容器，用来装Item类的对象
 5 
 6     //add方法，用来往媒体库里面添加东西
 7     public void add(Item item) {
 8         listItem.add(item);
 9     }
10 
11     //list方法，用来展示媒体库里面的东西    
12     public void list() {
13         for(Item item:listItem) {
14             item.print();
15         }
16     }
17     
18     public static void main(String[] args) {
19         Database db = new Database();
20         //往db里面添加MP3
21         db.add(new MP3("Faded",3,true,"...","Alan Walker",10));
22         db.add(new MP3("That Girl",4,true,"...","Olly Murs",10));
23         db.list();//列出db中的东西
24     }
25 
26 }
27 
28 public class Item {
29 //    定义Item类型的属性
30     private String title;
31     private int playingTime;
32     private boolean gotIt = false;
33     private String comment;
34     
35 //    构造函数，用来初始化Item类型的对象
36 //    可使用eclipse菜单栏中的Source\Generate Constructor Using Fields快速创建
37     public Item(String title, int playingTime, boolean gotIt, String comment) {
38         super();
39         this.title = title;
40         this.playingTime = playingTime;
41         this.gotIt = gotIt;
42         this.comment = comment;
43     }
44 
45 //    print方法
46     public void print() {
47         System.out.print(title+":"+playingTime+":"+gotIt+":"+comment);
48     }
49 }
50 
51 public class MP3 extends Item {
52 //    定义MP3类区别于父类Item的属性
53     private String artist;
54     private int numofTracks;
55 
56 //    构造函数
57 //    可使用eclipse菜单中Source/Generate Constructors from Superclass创建后修改
58     public MP3(String title, int playingTime, boolean gotIt, String comment,String artist,int numofTracks) {
59         super(title, playingTime, gotIt, comment);//括号内属性从父类获得初始化
60         this.artist=artist;
61         this.numofTracks=numofTracks;
62     }
63 
64 //    print方法
65     public void print() {
66         System.out.print("MP3:");
67         super.print();
68         System.out.println(":"+artist+":"+numofTracks);
69     }
70 }