From 3813621611945a0be23384c0c4d395b4c4a614ad Mon Sep 17 00:00:00 2001
From: pants <niklasjo2004@gmail.com>
Date: Mon, 21 Sep 2026 14:17:15 -0700
Subject: init

---
 java/MusicPlaylist.java | 135 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 135 insertions(+)
 create mode 100644 java/MusicPlaylist.java

(limited to 'java/MusicPlaylist.java')

diff --git a/java/MusicPlaylist.java b/java/MusicPlaylist.java
new file mode 100644
index 0000000..b127dd7
--- /dev/null
+++ b/java/MusicPlaylist.java
@@ -0,0 +1,135 @@
+// 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));
+        }
+    }
+}
-- 
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