4JavaPlaylist.java.txt

// Java code samples
// Created by Linh Ngo 
// For the Java2 class

// This is a Java class called "Playlist" that represents a playlist of songs.
// The class contains an array of songs, and methods for adding and removing songs from the playlist.
// Connected to Song.java.txt

import java.util.Arrays;


public class Playlist {
	private Song [] songs;
	private int numSongs;
	private static final int MIN_CAPACITY=3;
	private static final int EXPAND_THRESHOLD=4;
	private int expandBy =2;
	private int expandFrequency= 0; 
	
	// Constructor method that creates a new Playlist object with a default capacity of 3 songs.
	public Playlist()
	{
		songs= new Song[MIN_CAPACITY];
	}
	
	// Constructor method that creates a new Playlist object with the specified capacity.
	public Playlist(int capacity)
	{
		if(capacity<MIN_CAPACITY)
		{
			songs= new Song[MIN_CAPACITY];
		}
		else
		{
			songs= new Song[capacity];
		}
		
	}
	
	// Method that returns the current capacity of the playlist.
	public int getCapacity()
	{
		return songs.length;
	}
	
	// Method that returns the number of songs currently in the playlist.
	public int getNumSongs()
	{
		return numSongs;
	}
	
	// Method that returns the song at the specified index in the playlist.
	public Song getSong(int index)
	{
		if(index<0||index>songs.length-1)
		{
			return null;
		}
		else
		{
			return songs[index];
		}
	}
	
	// Method that returns a copy of the array of songs in the playlist.
	public Song[] getSongs()
	{
		Song[] newsongs= Arrays.copyOf(songs,numSongs);
		return newsongs;
	}
	
	// Method that expands the capacity of the playlist by a factor of 2 if the playlist has been expanded more than 4 times.
	public void expand()
	{
		if(expandFrequency>=EXPAND_THRESHOLD)
		{
			expandBy=expandBy*2;
		}
		
		Song[] newsonggs=Arrays.copyOf(songs,songs.length+expandBy);
		this.songs=newsonggs;
		expandFrequency+=1;
	}
	
	// Method that adds a new song to the playlist at the specified index.
	public boolean addSong(int index, Song song)
	{
		if(song==null||index<0||index>numSongs)
		{
			return false;
		}
		
		if(getCapacity()<getNumSongs()+1)
		{
			expand();
		}
			
		for(int i=numSongs;i>index;--i)
		{
			songs[i]=songs[i-1];
		}
		songs[index]=song;
		++ numSongs;
		
		return true;
			
	}
	
	// Method that adds a new song to the end of the playlist.
	public boolean addSong(Song song)
	{
		
		return addSong(numSongs,song);
	}
	
	// Method that adds all the songs from the specified playlist to the end of this playlist.
	public int addSongs(Playlist playlist)
	{
		
		
		if(playlist==null)
		{
			return 0;
		}
		
		int added= playlist.getNumSongs();
		
		{
		for(int i=0;i<added;++i)
		{
			if(playlist!=null)
			{
	
				addSong(playlist.getSong(i));
			}
		}
		}
		return added;
	}
	
	// Method that removes the song at the specified index from the playlist.
	public Song removeSong(int index)
	{
		
		if(getSong(index)==null)
		{
			return null;
		}
		
		Song remove= getSong(index);
		songs[index]=null;
			for(int i=index;i<numSongs-1;++i)
			{
				songs[i]=songs[i+1];
				
			}
		

		--numSongs;
		return remove;
	}
	
	// Method that removes the last song in the playlist.
	public Song removeSong()
	{
		return removeSong(numSongs-1);
	}
	
}