JAVA Linked lists You will be building a linked list. Make sure to keep track of

ID: 3575543 • Letter: J

Question

JAVA Linked lists

You will be building a linked list. Make sure to keep track of both the head and tail nodes.

(1) Create two files to submit.

SongEntry.java - Class declaration

Playlist.java - Contains main() method

Build the SongEntry class per the following specifications. Note: Some methods can initially be method stubs (empty methods), to be completed in later steps.

Private fields

String uniqueID - Initialized to "none" in default constructor

string songName - Initialized to "none" in default constructor

string artistName - Initialized to "none" in default constructor

int songLength - Initialized to 0 in default constructor

SongEntry nextNode - Initialized to null in default constructor

Default constructor (1 pt)

Parameterized constructor (1 pt)

Public member methods

insertAfter() (1 pt)

setNext() - Mutator (1 pt)

getID() - Accessor

getSongName() - Accessor

getArtistName() - Accessor

getSongLength() - Accessor

getNext() - Accessor

printPlaylistSongs()

Ex. of printPlaylistSongs output:

(2) In main(), prompt the user for the title of the playlist. (1 pt)

Ex:

(3) Implement the printMenu() method. printMenu() takes the playlist title as a parameter and outputs a menu of options to manipulate the playlist. Each option is represented by a single character. Build and output the menu within the method.

If an invalid character is entered, continue to prompt for a valid choice. Hint: Implement Quit before implementing other options. Call printMenu() in the main() method. Continue to execute the menu until the user enters q to Quit. (3 pts)

Ex:

(4) Implement "Output full playlist" menu option. If the list is empty, output: Playlist is empty (3 pts)

Ex:

(5) Implement the "Add song" menu item. New additions are added to the end of the list. (2 pts)

Ex:

(6) Implement the "Remove song" method. Prompt the user for the unique ID of the song to be removed.(4 pts)

Ex:

(7) Implement the "Change position of song" menu option. Prompt the user for the current position of the song and the desired new position. Valid new positions are 1 - n (the number of nodes). If the user enters a new position that is less than 1, move the node to the position 1 (the head). If the user enters a new position greater than n, move the node to position n (the tail). 6 cases will be tested:

Moving the head node (1 pt)

Moving the tail node (1 pt)

Moving a node to the head (1 pt)

Moving a node to the tail (1 pt)

Moving a node up the list (1 pt)

Moving a node down the list (1 pt)

Ex:

(8) Implement the "Output songs by specific artist" menu option. Prompt the user for the artist's name, and output the node's information, starting with the node's current position. (2 pt)

Ex:

(9) Implement the "Output total time of playlist" menu option. Output the sum of the time of the playlist's songs (in seconds). (2 pts)

Ex:

Explanation / Answer

PROGRAM CODE:

SongEntry.java

package playlist;

public class SongEntry {

private String uniqueID;

private String songName;

private String artistName;

private int songLength;

SongEntry nextNode;

SongEntry()

{

uniqueID = "";

songName = "";

artistName = "";

songLength = 0;

nextNode = null;

}

SongEntry(String uniqueID, String songName, String artistName, int songLength)

{

this.uniqueID = uniqueID;

this.songName = songName;

this.songLength = songLength;

this.artistName = artistName;

this.nextNode = null;

}

public void insertAfter( SongEntry entry)

{

SongEntry entries = this;

while(entries.nextNode != null)

{

entries = entries.nextNode;

}

entries.nextNode = entry;

}

public void setNext(SongEntry entry){

this.nextNode = entry;

}

public void setUniqueID(String uniqueID) {

this.uniqueID = uniqueID;

}

public void setSongName(String songName) {

this.songName = songName;

}

public void setArtistName(String artistName) {

this.artistName = artistName;

}

public void setSongLength(int songLength) {

this.songLength = songLength;

}

public void setNextNode(SongEntry nextNode) {

this.nextNode = nextNode;

}

public String getID()

{

return this.uniqueID;

}

public String getSongName()

{

return this.songName;

}

public String getArtistName()

{

return this.artistName;

}

public int getSongLength()

{

return this.songLength;

}

public SongEntry getNext()

{

return this.nextNode;

}

public void printPlaylistSongs()

{

System.out.println("Unique ID: "+getID());

System.out.println("Song Name: "+getSongName());

System.out.println("Artist Name: "+getArtistName());

System.out.println("Song Length(in seconds): "+getSongLength());

}

Playlist.java

package playlist;

import java.util.Scanner;

public class Playlist {

public static Scanner sc = new Scanner(System.in);
public static Scanner scInt = new Scanner(System.in);
public static SongEntry headSong = new SongEntry();
public static SongEntry tailSong = new SongEntry();
public static SongEntry allEntries;
public static int numberOfNodes = 0;

public static void printMenu(String playlistTitle)

{
System.out.println(" "+playlistTitle.toUpperCase()+" PLAYLIST MENU");
System.out.println("a - Add song d - Remove song c - Change position of song s - Output songs by specific artist");
System.out.println("t - Output total time of playlist (in seconds) o - Output full playlist q - Quit");
System.out.println(" Choose an option: ");
String option = sc.next();
boolean isEnter = option.equals("a") || option.equals("d") || option.equals("c") || option.equals("s") || option.equals("t") || option.equals("o") || option.equals("q");

if(isEnter)
{
switch(option.charAt(0))
{
case 'a': addSong();
printMenu(playlistTitle);
break;

case 'd': if(!isPlayListEmpty())
            {
           allEntries = removeSong(allEntries);
              numberOfNodes--;
              printMenu(playlistTitle);
       }
                break;

case 'c': if(!isPlayListEmpty())
       {
              allEntries = changeSongPosition(allEntries);
              printMenu(playlistTitle);
       }
            break;

case 's': if(!isPlayListEmpty())
            {
              songsBySpecificArtist(allEntries);
              printMenu(playlistTitle);
            }
            break;

case 't': if(!isPlayListEmpty())
       {
           totalTimeofPlaylist(allEntries);
              printMenu(playlistTitle);
       }
            break;

case 'o': System.out.println(playlistTitle.toUpperCase() + " - OUTPUT FULL PLAYLIST");
           outputFullPlaylist(allEntries);
           printMenu(playlistTitle);
           break;

case 'q': break;

}

else

{

System.out.println("Invalid Choice !");

printMenu(playlistTitle);

}

public static boolean isPlayListEmpty()
{
   boolean isEmpty = false;

   if(numberOfNodes<=0)
   {
       System.out.println("Playlist is empty ");
       isEmpty = true;
   }
   return isEmpty;
}

public static void outputFullPlaylist(SongEntry entries)

{

int counter = 1;

if(entries != null)

{

System.out.println(counter+".");

entries.printPlaylistSongs(); // head node

counter++;

while(entries.nextNode != null) // all the remaining nodes

{

entries = entries.nextNode;

System.out.println(counter+".");

entries.printPlaylistSongs();

counter++;

}

else

{

System.out.println("Playlist is empty");

}

public static void addSong()

{

sc = new Scanner(System.in);

System.out.println("ADD SONG");

System.out.println("Enter song's Unique ID: ");

String songID = sc.next();

sc = new Scanner(System.in);

System.out.println("Enter song's name: ");

String songname = sc.nextLine();

sc = new Scanner(System.in);

System.out.println("Enter artist's name: ");

String artistName = sc.nextLine();

System.out.println("Enter song's length(in seconds): ");

int songlength = scInt.nextInt();

SongEntry entry = new SongEntry(songID, songname, artistName, songlength);

if(allEntries == null)

{

headSong = entry; // this is the head

allEntries = entry;

tailSong = entry; // this is the tail

numberOfNodes++;

}

else

{

allEntries.insertAfter(entry);

tailSong = entry;

numberOfNodes++;

}

public static SongEntry removeSong(SongEntry entries)

{

System.out.println("Enter the song's unique ID: ");

String id = sc.next();

SongEntry newEntry = null, entry=null;

int counter = 0;

while(counter<numberOfNodes)

{

if(!entries.getID().equals(id))

{

newEntry = new SongEntry();

newEntry.setUniqueID(entries.getID());

newEntry.setSongName(entries.getSongName());

newEntry.setArtistName(entries.getArtistName());

newEntry.setSongLength(entries.getSongLength());

if(entry == null)

entry = newEntry;

else

entry.insertAfter(newEntry);

}

else

{

System.out.println(""" + entries.getSongName()+"" removed");

}

entries = entries.nextNode;

counter++;

}

return entry;

}

public static SongEntry changeSongPosition(SongEntry entries)

{

   if(numberOfNodes<=1)
   {
       System.out.println("There is only one song in the playlist");
       return entries;
   }
   System.out.println("CHANGE POSITION OF SONG");
   System.out.println("ENTER song's current position: ");
   int currentPos = scInt.nextInt();
   System.out.println("Enter new position of song: ");
   int newPos = scInt.nextInt();
   SongEntry currentPosEntry = null, entry = null, newPosEntry = null, returnEntry = null;
   entry = entries;
   int counter = 1;

   if(newPos<1)
   newPos = 1;
   else if(newPos>numberOfNodes)
   newPos = numberOfNodes;

   entry = entries;
   for(int i=1; i<=numberOfNodes; i++)
   {
   if(i==currentPos)
   currentPosEntry = entries;

   else if(i==newPos)
   newPosEntry = entries;

   entries = entries.nextNode;
   }

//entries = entry;


   while(counter<=numberOfNodes)
   {
       SongEntry internalEntry = new SongEntry();
       if(counter == currentPos)
       {
           internalEntry.setUniqueID(newPosEntry.getID());
           internalEntry.setArtistName(newPosEntry.getArtistName());
           internalEntry.setSongLength(newPosEntry.getSongLength());
           internalEntry.setSongName(newPosEntry.getSongName());
       }
       else if(counter == newPos)
       {
           internalEntry.setUniqueID(currentPosEntry.getID());
           internalEntry.setArtistName(currentPosEntry.getArtistName());
           internalEntry.setSongLength(currentPosEntry.getSongLength());
           internalEntry.setSongName(currentPosEntry.getSongName());
       }
       else
       {
           internalEntry.setUniqueID(entry.getID());
           internalEntry.setArtistName(entry.getArtistName());
           internalEntry.setSongLength(entry.getSongLength());
           internalEntry.setSongName(entry.getSongName());
       }

       if(returnEntry == null)
           returnEntry = internalEntry;
       else
           returnEntry.insertAfter(internalEntry);
       entry = entry.nextNode;
       counter++;
   }
      System.out.println(""" + currentPosEntry.getSongName() + """ + " moved to position " + newPos);

return returnEntry;

}

public static void totalTimeofPlaylist(SongEntry entries)

{

System.out.println("OUTPUT TOTAL TIME OF PLAYLIST (IN SECONDS)");

int totalSeconds = entries.getSongLength();

entries = entries.nextNode;

while(entries != null)

{

totalSeconds += entries.getSongLength();

entries = entries.nextNode;

}

System.out.println("Total Time: "+totalSeconds+" seconds");

}

public static void songsBySpecificArtist(SongEntry entries)

{

sc = new Scanner(System.in);

System.out.println("OUTPUT SONGS BY SPECIFIC ARTIST");

System.out.println("Enter artist's name: ");

String artistname = sc.nextLine();

while(entries != null)

{

if(entries.getArtistName().equals(artistname))

{

entries.printPlaylistSongs();

}

entries = entries.nextNode;

}

/**

* @param args

public static void main(String[] args) {

System.out.println("Enter playlist's title: ");

sc = new Scanner(System.in);

String title = sc.nextLine();

printMenu(title);

}

OUTPUT:

Enter playlist's title:
jmz