Added 'Node' class

Node.java

@@ -0,0 +1,47 @@
+import java.io.ObjectInputStream;
+import java.io.FileInputStream;
+import java.io.ObjectOutputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.Serializable;
+import java.util.HashMap;
+
+public class Node implements Serializable {
+
+    private static final FILENAME = "data";
+
+    protected HashMap<Integer, MusicObject> data;
+
+
+    public Node() { 
+        this.data = new HashMap<Integer, MusicObject>();
+    }
+
+    public void addMusicObject(MusicObject song) {
+        this.data.put(song.getId(), song); 
+    }
+
+    protected void writeToFile() {
+        try {
+            FileOutputStream fos = new FileOutputStream(FILENAME);
+            ObjectOutputStream oos = new ObjectOutputStream(fos);
+
+            oos.write(this.data);
+
+            oos.close();
+            fos.close();
+        } catch (IOException e) { e.printStackTrace(); }
+    }
+
+    protected void readFromFile() {
+        try {
+            FileInputStreaInputStream fis = new FileInputStream(FILENAME);
+            ObjectInputStream ois = new ObjectInputStream(fis);
+
+            this.data = (HashMap<Integer, MusicObject>)ois.read(data);
+
+            oos.close();
+            fos.close();
+        } catch (IOException e) { e.printStackTrace(); }
+    }
+}