niklasjohnson/java/MusicPlaylist.java

// Nik Johnson
// 1-31-2024
// TA: Andy Ruan

import java.util.*;

// music playlist manager with functionality to add and play songs while keeping track of play history,
// which can be cleared, or deleted from in batches
public class MusicPlaylist {

    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        Queue<String> playlist = new LinkedList<>();
        Stack<String> history = new Stack<>();
        System.out.println("Welcome to the CSE 122 Music Playlist!");
    
        String destination = navigator(console);
        while (!destination.equalsIgnoreCase("Q")) {
            if (destination.equalsIgnoreCase("A")) {
                addSong(console, playlist);
            } else if (destination.equalsIgnoreCase("P")) {
                playSong(playlist, history);
            } else if (destination.equalsIgnoreCase("Pr")) {
                printHistory(history);
            } else if (destination.equalsIgnoreCase("C")) {
                clearHistory(history);
            } else if (destination.equalsIgnoreCase("D")) {
                deleteFromHistory(console, history);
            }
            destination = navigator(console);
        }
    }

    // menu function, called initially and after any other functions
    // return String for use in main menu loop
    public static String navigator(Scanner console) {
        System.out.println("(A) Add song");
        System.out.println("(P) Play song");
        System.out.println("(Pr) Print history");
        System.out.println("(C) Clear history");
        System.out.println("(D) Delete from history");
        System.out.println("(Q) Quit");
        System.out.println();
        System.out.print("Enter your choice: ");
        String destination = console.nextLine();
        return destination;
    }

    // add song to playlist according to user input
    // no return
    public static void addSong(Scanner console, Queue<String> playlist) {
        System.out.print("Enter song name: ");
        String songToAdd = console.nextLine();
        playlist.add(songToAdd);
        System.out.println("Successfully added " + songToAdd);
        System.out.println();
        System.out.println();
    }
    
    //  play song at the front of the playlist
    //  no return
    public static void playSong(Queue<String> playlist, Stack<String> history) {
        // if user attempts to play song when playlist is empty, throw exception
        if (playlist.isEmpty()) throw new IllegalStateException();
        String songToPlay = playlist.remove();
        System.out.println("Playing song: " + songToPlay);
        history.push(songToPlay);
        System.out.println();
        System.out.println();
    }

    // print history of played songs
    // return unmodified history after printing it
    public static void printHistory(Stack<String> history) {
        int size = history.size();
        // if there is no history and user attempts to print history, throw exception
        if (history.isEmpty()) throw new IllegalStateException();
        String[] historyArray = new String[size];
        if (size != 0) {
            for (int i = (size - 1); i >= 0; i--) {
                historyArray[i] = history.pop();
                System.out.println("    " + historyArray[i]);
            }
            for (int n = 0; n < size; n++) {
                history.push(historyArray[n]);
            }
        }
        System.out.println();
        System.out.println();
    }

    // clear history when called
    // return empty history
    public static void clearHistory(Stack<String> history) {
        history.clear();
    }
    
    // delete from history according to user input, starting either from most recent or oldest history
    // return modified history
    public static void deleteFromHistory(Scanner console, Stack<String> history) {
        int size = history.size();
        List<String> historyArrayList = new ArrayList<>();
        if (!history.isEmpty()) {
            for (int i = 0; i < size; i++) {
                historyArrayList.add(history.pop());
            }
        }
        System.out.println("A positive number will delete from recent history.");
        System.out.println("A negative number will delete from the beginning of history.");
        System.out.print("Enter number of songs to delete: ");
        int numToDelete = Integer.parseInt(console.nextLine());
        int absNum = Math.abs(numToDelete);
        if (absNum > size) {
            throw new IllegalArgumentException();
        }
        System.out.println();
        if (size != 0 && absNum != 0) {
            if (absNum == size) {
                historyArrayList.clear();
            } else if (numToDelete < 0) {
                int lastIndex = size - 1;
                for (int n = lastIndex; n >= (size - absNum); n--) {
                    historyArrayList.remove(n);
                }
            } else if (numToDelete > 0) {
                for (int i = 0; i < numToDelete; i++) {
                    historyArrayList.remove(0);
                }
            }
        }
        for (int n = (historyArrayList.size() - 1); n >= 0; n--) {
            history.push(historyArrayList.get(n));
        }
    }
}