Java进阶学习（4）之继承与多态.demo

多媒体数据库小练习

 package com.dome;

 import java.util.ArrayList;

 public class Database
 {

 //    private ArrayList<CD> listCD=new ArrayList<CD>();
 //    private ArrayList<DVD> listDVD=new ArrayList<DVD>();
     private ArrayList<Iterm> listIterm=new ArrayList<Iterm>();

 //    public void add(CD cd)
 //    {
 //        listCD.add(cd);
 //    }
 //
 //    public void add(DVD dvd)
 //    {
 //        listDVD.add(dvd);
 //    }
     public void add(Iterm iterm)
     {
         listIterm.add(iterm);
     }

     public void list()
     {
 //        for (CD cd : listCD)
 //        {
 //            cd.print();
 //        }
 //        for (DVD dvd : listDVD)
 //        {
 //            dvd.print();
 //        }
         for (Iterm iterm : listIterm)
         {
             iterm.print();
         }
     }

     public static void main(String[] args)
     {
         // TODO Auto-generated method stub

 //        Database db=new Database();
 //        db.add(new CD("abc", "abc", 4, 60, "..."));
 //        db.add(new CD("def", "def", 4, 60, "..."));
 //        db.add(new DVD("xxx","xxx",120,"..."));
 //        db.list();
         Iterm i=new Iterm("a", 3, false, "..");
         i.print();
     }

 }

Iterm类

package com.dome;

public class Iterm
{

    private String title;
    private int playingTime;
    private  boolean gotIt = false;
    private String comment;

    public Iterm(String title, int playingTime, boolean gotIt, String comment)
    {
        super();
        this.title = title;
        this.playingTime = playingTime;
        this.gotIt = gotIt;
        this.comment = comment;
    }

    protected void print()
    {
        // TODO Auto-generated method stub
        System.out.print(title);
    }

}

CD类

 package com.dome;

 public class CD extends Iterm
 {

     private String artist;
     private int numofTracks;

     public CD(String title, String artist, int numofTracks, int playingTime, String comment)
     {
         super(title,playingTime,false,comment);
 //        this.title = title;
         this.artist = artist;
         this.numofTracks = numofTracks;
     }

     public static void main(String[] args)
     {
         // TODO Auto-generated method stub

     }

     public void print()
     {
         // TODO Auto-generated method stub
         System.out.print("CD:");
         super.print();
         System.out.println(":"+artist);
     }
 }

DVD类

 package com.dome;

 public class DVD extends Iterm
 {

     private String director;

     public DVD(String title, String director, int playingTime, String comment)
     {
         super(title, playingTime, false, comment);
         this.director = director;
     }

     public static void main(String[] args)
     {
         // TODO Auto-generated method stub

     }

     public void print()
     {
         // TODO Auto-generated method stub
         System.out.print("CD:");
         super.print();
         System.out.print(":"+director);
     }

 }

总结：通过这次小练习，体会了代码重复的危害和继承和函数的好处。