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Semester 1/Programming 1/Java/examples/projects/chapter13/musicplayer/MusicPlayer.java

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+import java.io.BufferedInputStream;
+import java.io.FileInputStream;
+import java.io.InputStream;
+import java.io.IOException;
+import javazoom.jl.decoder.JavaLayerException;
+import javazoom.jl.player.AudioDevice;
+import javazoom.jl.player.FactoryRegistry;
+
+/**
+ * Provide basic playing of MP3 files via the javazoom library.
+ * See http://www.javazoom.net/
+ * 
+ * @author David J. Barnes and Michael Kölling
+ * @version 2016.02.29
+ */
+public class MusicPlayer
+{
+    // The current player. It might be null.
+    private MusicFilePlayer player;
+    // The current file being played.
+    private String filename;
+    
+    /**
+     * Constructor for objects of class MusicPlayer
+     */
+    public MusicPlayer()
+    {
+        player = null;
+        filename = "";
+    }
+    
+    /**
+     * Start playing the given audio file.
+     * The method returns once the playing has been started.
+     * @param filename The file to be played.
+     */
+    public void startPlaying(final String filename)
+    {
+        try {
+            setupPlayer(filename);
+            playFrom(0);
+        }
+        catch (JavaLayerException ex) {
+            reportProblem();
+        }
+    }
+    
+    /**
+     * Stop playing the current file.
+     */
+    public void stop()
+    {
+        killPlayer();
+    }
+    
+    /**
+     * Pause the current file.
+     */
+    public void pause()
+    {
+        if(player != null) {
+            try {
+                player.pause();
+            }
+            catch(JavaLayerException e) {
+                reportProblem();
+                killPlayer();
+            }
+        }
+    }
+    
+    /**
+     * Resume playing following a pause.
+     */
+    public void resume()
+    {
+        if(player != null) {
+            Thread playerThread = new Thread() {
+                public void run()
+                {
+                    try {
+                        player.resume();
+                    }
+                    catch(JavaLayerException e) {
+                        reportProblem();
+                        killPlayer();
+                    }
+                }
+            };
+            playerThread.setPriority(Thread.MIN_PRIORITY);
+            playerThread.start();
+        }
+    }
+    
+    /**
+     * Seek to the given position in the current file.
+     * The track will be paused as a result of this operation.
+     * 
+     * @param position What position in the file to move to.
+     */
+    public void seekTo(int position)
+    {
+        if(player != null && position >= 0 && position < player.getLength()) {
+            // Set the player's position.
+        }
+            
+    }
+    
+    /**
+     * Return the length of the current music file, if any.
+     * The length is in 'frames' rather than seconds, for instance.
+     * 
+     * @return The file length in frames.
+     */
+    public int getLength()
+    {
+        if(player != null) {
+            return player.getLength();
+        }
+        else {
+            return 0;
+        }
+    }
+    
+    /**
+     * Set up the player ready to play the given file.
+     * @param filename The name of the file to play.
+     */
+    private void setupPlayer(String filename)
+    {
+        try {
+            if(player != null) {
+                killPlayer();
+            }
+            this.filename = filename;
+            player = new MusicFilePlayer(filename);
+        }
+        catch(JavaLayerException e) {
+            System.out.println("Problem setting up player");
+            e.printStackTrace();
+            reportProblem();
+            killPlayer();
+        }
+    }
+    
+    /**
+     * Play from the given position.
+     * @param start The starting position for playing.
+     *              Must be within the current file's length.
+     */
+    private void playFrom(final int start) throws JavaLayerException
+    {
+        Thread playerThread = new Thread() {
+            public void run()
+            {
+                try {
+                    player.playFrom(start);
+                }
+                catch(JavaLayerException e) {
+                    reportProblem();
+                    killPlayer();
+                }
+            }
+        };
+        playerThread.setPriority(Thread.MIN_PRIORITY);
+        playerThread.start();
+    }
+
+    /**
+     * Terminate the player, if there is one.
+     */
+    private void killPlayer()
+    {
+        synchronized(this) {
+            if(player != null) {
+                player.stop();
+                player = null;
+                filename = "";
+            }
+        }
+    }
+    
+    /**
+     * Report a problem playing the current file.
+     */
+    private void reportProblem()
+    {
+        System.out.println("There was a problem playing: " + filename);
+    }
+
+}