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。