songcollectionimpl.java

Java的面向对象数据库系统的源代码

package song;

// $Id: song.SongCollectionImpl.java,v 1.1 2002/05/17 08:28:18 per_nyfelt Exp $



import org.ozoneDB.OzoneObject;

import java.util.AbstractMap;
import java.util.TreeMap;

/**
 * Persistenet object that represents a catalog of Songs.
 *
 * @version $Revision: 1.1 $
 * @author James Stiefel
 */
public class SongCollectionImpl extends OzoneObject implements SongCollection {

    /**
     * The serialization version id used by the Java serialization.
     */
    final static long serialVersionUID = 1L;


    TreeMap      songMap = new TreeMap();

    /**
     * Adds a song.Song to the song.SongCollection
     *
     */
    public void addSong(String title, Song song) throws Exception {
        Song old = (Song) songMap.put(title, song);
        if (old != null) {
            System.out.println("song.SongCollection.addSong: song already exists, not added : " + title);
            songMap.put(old.getTitle(), old);

            throw new  Exception ("Duplicate song title");
        }
    }


    /**
     * Deletes a song.Song from the song.SongCollection and database
     *
     */
    public Song deleteSong(String  title) {
        Song song = null;
        try{
            song = (Song)songMap.remove(title);
            if (song != null){
                database().deleteObject(song);
            }
        } catch (Exception e) {
            System.out.println("Failure removing song.");
            e.printStackTrace();
        }
        return null;
    }

    /**
     * Finds a song in song.SongCollection
     *
     */
    public Song findSong(String song_title) {
        return (Song)songMap.get(song_title);
    }

    /**
     * Returns the collection of Songs represented by
     * this song.SongCollection.
     *
     */
    public AbstractMap getAllSongs(){
        return songMap;
    }

}