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How to implement Iterator Design Pattern in Java ?.

Program to demonstrate how to implement Iterator Design Pattern in Java.

1. Song.java
package com.hubberspot.designpattern.behavioral.iterator;

public class Song {

    private String songName;
    private String singer;

    public Song(String songName, String singer) {
        super();
        this.songName = songName;
        this.singer = singer;
    }    

    public String getSongName() {
        return songName;
    }
    public String getSinger() {
        return singer;
    }

}



2. SongCollection.java
package com.hubberspot.designpattern.behavioral.iterator;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class SongCollection {

    private List< Song > songList = new ArrayList< Song >();

    public void addSong(Song song) {
        songList.add(song);
    }

    public Iterator< Song > getSongIterator() {

        return new SongIterator();
    } 

    private class SongIterator implements Iterator< Song > {

        int currentSongIndex = 0;

        @Override
        public boolean hasNext() {
            if (currentSongIndex >= songList.size()) {
                return false;
            } else {
                return true;
            }
        }

        @Override
        public Song next() {

            return songList.get(currentSongIndex++);

        }

        @Override
        public void remove() {

            songList.remove(--currentSongIndex);

        }

    }
}



3. SongIterationDemo.java
package com.hubberspot.designpattern.behavioral.iterator;

import java.util.Iterator;

public class SongIterationDemo {

    public static void main(String[] args) {

        Song s1 = new Song("Rock You !!!" , "Eric Martin");        
        Song s2 = new Song("Someone Gone !!!" , "Neuone Derek");        
        Song s3 = new Song("Remember Me !!!" , "Justin Diebler");        

        SongCollection songCollection = new SongCollection();
        songCollection.addSong(s1);
        songCollection.addSong(s2);
        songCollection.addSong(s3);

        System.out.println("Displaying Song Info : \n");
        Iterator< Song > songIterator = songCollection.getSongIterator();

        while(songIterator.hasNext()) {
            Song song = songIterator.next();
            System.out.println("Song Name : " + song.getSongName());
            System.out.println("Song Singer : " + song.getSinger());
            System.out.println();
        }

        System.out.println("Removing Song and Displaying :\n");

        songIterator.remove();

        songIterator = songCollection.getSongIterator();

        while(songIterator.hasNext()) {
            Song song = songIterator.next();
            System.out.println("Song Name : " + song.getSongName());
            System.out.println("Song Singer : " + song.getSinger());
            System.out.println();
        }
    }
}



Output of the program : 


 
 
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