Question

Complete the required methods:

public class SongList
{
// instance variables
private Song m_last;
private int m_numElements;

// constructor
// Do not make any changes to this method!
public SongList()
{
m_last = null;
m_numElements = 0;
}

// check whether the list is empty
// Do not make any changes to this method!
boolean isEmpty()
{
if (m_last == null)
return true;
else
return false;
}

// return the size of the list (# of Song nodes)
// Do not make any changes to this method!
public int size()
{
return m_numElements;
}

// add a new Song to the circular linked list with the given artist and
// title, keeping the list sorted by *song title*.
public void add(String artist, String title)
{
// TODO: implement this method
}

// remove a Song associated with the given artist and title from the list,
// keeping the list sorted by *song title*.
public boolean remove(String artist, String title)
{
// TODO: implement this method
}
  
  
// build and return a circular linked list that contains all songs from the
// given artist
public SongList buildList(String artist)
{
// TODO: implement this method
}
  
// return a string representation of the list
// Do not make any changes to this method!
public String toString()
{   
String listContent = "";
Song current = m_last;
  
if (m_last != null)
do
{
current = current.getLink();
listContent += " [" + current.getArtist() + " - " + current.getTitle() + "]\n";

} while (current != m_last);

return listContent;
}
}

// The Song class that represents a song
// Do not make any changes to this file!

public class Song
{
// instance variables
private String m_artist;
private String m_title;
private Song m_link;

// constructor
public Song(String artist, String title)
{
m_artist = artist;
m_title = title;
m_link = null;
}

// getters and setters
public void setArtist(String artist)
{
m_artist = artist;
}

public String getArtist()
{
return m_artist;
}

public void setTitle(String title)
{
m_title = title;
}

public String getTitle()
{
return m_title;
}
  
public void setLink(Song link)
{
m_link = link;
}

public Song getLink()
{
return m_link;
}
}

Answer 1

Program Code Screenshot (SongList.java)

Program Code Screenshot (Main.java) for testing

Program Sample Input/Output Screenshot

Program Code to Copy (SongList.java)

public class SongList {
    // instance variables
    private Song m_last;
    private int m_numElements;

    // constructor
    // Do not make any changes to this method!
    public SongList() {
        m_last = null;
        m_numElements = 0;
    }

    // check whether the list is empty
    // Do not make any changes to this method!
    boolean isEmpty() {
        if (m_last == null)
            return true;
        else
            return false;
    }

    // return the size of the list (# of Song nodes)
    // Do not make any changes to this method!
    public int size() {
        return m_numElements;
    }

    // add a new Song to the circular linked list with the given artist and
    // title, keeping the list sorted by *song title*.
    public void add(String artist, String title) {
        // check for first insertion
        if (m_last == null) {
            m_last = new Song(artist, title);
            m_last.setLink(m_last);
            m_numElements++;
        } else {
            // find sorted position of insertion
            Song temp = m_last;
            while (!temp.getLink().equals(m_last) && temp.getLink().getTitle().compareTo(title) < 0) {
                temp = temp.getLink();
            }
            // create element
            Song newSong = new Song(artist, title);
            // insert after temp
            newSong.setLink(temp.getLink());
            temp.setLink(newSong);
            m_last=temp.getLink();
            // update number of elements
            m_numElements++;
        }
    }

    // remove a Song associated with the given artist and title from the list,
    // keeping the list sorted by *song title*.
    public boolean remove(String artist, String title) {
        //check if it is the m_last element
        if(m_last.getTitle().equals(title) && m_last.getArtist().equals(artist)){
            Song temp = m_last;
            // if m_las is the only element 
            if(temp.getLink()==m_last){
                m_last=null;
            }else{
                //get new m_last
                while(!temp.getLink().equals(m_last)){
                    temp=temp.getLink();
                }
                //update temp->link
                temp.setLink(m_last.getLink());
            }
            m_numElements--;
            return true;
        }
        //search for the element to remove
        Song temp = m_last;
        while(!temp.getLink().equals(m_last) && !(temp.getLink().getArtist().equals(artist) && temp.getLink().getTitle().equals(title))){
            temp=temp.getLink();
        }
        System.out.println(temp.getTitle());
        if(temp.getLink().equals(m_last)){
            return false;
        }else{
            temp.setLink(temp.getLink().getLink());
            m_numElements--;
            return true;
        }
    }

    // build and return a circular linked list that contains all songs from the
    // given artist
    public SongList buildList(String artist) {
        // create a list
        SongList list = new SongList();

        // check if no element in list
        if(m_last==null){
            return list;
        }

        //check if we should add m_last
        if(m_last.getArtist().equals(artist)){
            list.add(artist, m_last.getTitle());
        }

        //keep searching in our list and add in new list if artist matches
        Song temp = m_last.getLink();

        while(!temp.equals(m_last)){
            if(temp.getArtist().equals(artist)){
                list.add(artist, temp.getTitle());
            }
            temp=temp.getLink();
        }
        return list;
    }

    // return a string representation of the list
    // Do not make any changes to this method!
    public String toString() {
        String listContent = "";
        Song current = m_last;

        if (m_last != null)
            do {
                current = current.getLink();
                listContent += " [" + current.getArtist() + " - " + current.getTitle() + "]\n";

            } while (current != m_last);

        return listContent;
    }
}

Program Code to Copy (Main.java)

class Main {
    public static void main(String[] args) {
        //test SongList
        SongList list = new SongList();

        //test add
        list.add("Ed Sheeran", "Shape of You");
        list.add("Juston Bieber", "Holy");
        list.add("Ed Sheeran", "Perfect");
        list.add("Ed Sheeran", "I Don't Care");
        list.add("Ludacris", "Love Me");

        System.out.println("List after addition : \n"+list);

        //test delete
        list.remove("Ed Sheeran", "Perfect");
        System.out.println("List after removing (Ed Sheeran, Perfect) : \n"+list);

        //test building list
        list = list.buildList("Juston Bieber");
        System.out.println("List built for artist Juston Bieber : \n"+list);
    }
}