clean code: extract inner classes

src/main/java/eu/midnightdust/yaytris/Tetris.java

@@ -3,7 +3,8 @@ package eu.midnightdust.yaytris;
 import eu.midnightdust.yaytris.game.Space;
 import eu.midnightdust.yaytris.ui.ScoreMenu;
 import eu.midnightdust.yaytris.ui.TetrisUI;
-import eu.midnightdust.yaytris.util.SoundUtil;
+import eu.midnightdust.yaytris.util.GravityTimerTask;
+import eu.midnightdust.yaytris.util.sound.SoundUtil;
 
 import javax.swing.*;
 import java.time.LocalTime;
@@ -48,6 +49,15 @@ public class Tetris {
         return space;
     }
 
+    /**
+     * Get the ui instance
+     *
+     * @see          TetrisUI
+     */
+    public static TetrisUI getUi() {
+        return ui;
+    }
+
     /**
      * Resets the game space, preparing it for a new game.
      *
@@ -127,17 +137,4 @@ public class Tetris {
         }
     }
 
-    /**
-     * Defines our custom timer task that handles falling pieces.
-     */
-    public static class GravityTimerTask extends TimerTask {
-        @Override
-        public void run() {
-            if (space.getCurrentTetromino() != null) {
-                updateTime();
-                space.getCurrentTetromino().fall();
-                ui.getGamePanel().repaint();
-            }
-        }
-    }
 }

src/main/java/eu/midnightdust/yaytris/util/GravityTimerTask.java

@@ -0,0 +1,19 @@
+package eu.midnightdust.yaytris.util;
+
+import eu.midnightdust.yaytris.Tetris;
+
+import java.util.TimerTask;
+
+/**
+ * Defines our custom timer task that handles falling pieces.
+ */
+public class GravityTimerTask extends TimerTask {
+    @Override
+    public void run() {
+        if (Tetris.getSpace().getCurrentTetromino() != null) {
+            Tetris.updateTime();
+            Tetris.getSpace().getCurrentTetromino().fall();
+            Tetris.getUi().getGamePanel().repaint();
+        }
+    }
+}

src/main/java/eu/midnightdust/yaytris/util/SoundEffect.java

@@ -1,5 +1,7 @@
 package eu.midnightdust.yaytris.util;
 
+import eu.midnightdust.yaytris.util.sound.SoundUtil;
+
 public enum SoundEffect {
     BOOP("/sounds/boop.wav"), LINE_COMPLETED("/sounds/line-completed.wav");
 

src/main/java/eu/midnightdust/yaytris/util/sound/LineUpdateListener.java

@@ -0,0 +1,13 @@
+package eu.midnightdust.yaytris.util.sound;
+
+import javax.sound.sampled.LineEvent;
+import javax.sound.sampled.LineListener;
+
+public class LineUpdateListener implements LineListener {
+    @Override
+    public void update(LineEvent event) {
+        if (LineEvent.Type.STOP == event.getType()) {
+            event.getLine().close();
+        }
+    }
+}

src/main/java/eu/midnightdust/yaytris/util/sound/MusicThread.java

@@ -0,0 +1,70 @@
+package eu.midnightdust.yaytris.util.sound;
+
+import eu.midnightdust.yaytris.Settings;
+
+import javax.sound.sampled.*;
+import java.io.IOException;
+
+/**
+ * Handle music in separate threads to not interrupt the main game
+ */
+public class MusicThread extends Thread {
+    private static final int BUFFER_SIZE = 8192;
+    private final boolean looped;
+    private final String fileLocation;
+    private boolean playing;
+
+    public MusicThread(String fileLocation, boolean looped) {
+        this.fileLocation = fileLocation;
+        this.looped = looped;
+        this.playing = true;
+    }
+
+    public void stopMusic() {
+        this.playing = false;
+    }
+
+    @Override
+    public void run() {
+        do {
+            playMusic(fileLocation);
+        } while (looped && playing);
+    }
+
+    /**
+     * INTERNAL!
+     * Play the long audio file found at the specified location.
+     * Fades out after calling {@link #stopMusic()}.
+     * Adapted from: <a href="https://www.baeldung.com/java-play-sound">Baeldung</a>
+     *
+     * @see SoundUtil#playMusic(String, boolean)
+     */
+    private void playMusic(String fileLocation) {
+        try (AudioInputStream stream = AudioSystem.getAudioInputStream(SoundUtil.getResource(fileLocation))) {
+            AudioFormat format = stream.getFormat();
+            DataLine.Info info = new DataLine.Info(SourceDataLine.class, format);
+
+            SourceDataLine sourceDataLine = (SourceDataLine) AudioSystem.getLine(info);
+            sourceDataLine.open(format);
+            sourceDataLine.start();
+            SoundUtil.setVolume(sourceDataLine, Settings.musicVolume);
+            float fadeOut = 1.0f;
+
+            byte[] bufferBytes = new byte[BUFFER_SIZE];
+            int readBytes;
+            while ((readBytes = stream.read(bufferBytes)) != -1) {
+                if (!playing) {
+                    fadeOut = (float) Math.sin(fadeOut - 0.01f); // Sinus fade-out
+                    SoundUtil.setVolume(sourceDataLine, (int) (fadeOut * Settings.musicVolume));
+                    if (fadeOut <= 0) break;
+                }
+                sourceDataLine.write(bufferBytes, 0, readBytes);
+            }
+
+            sourceDataLine.drain();
+            sourceDataLine.close();
+        } catch (LineUnavailableException | IOException | UnsupportedAudioFileException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}

src/main/java/eu/midnightdust/yaytris/util/sound/SoundUtil.java

@@ -1,4 +1,4 @@
-package eu.midnightdust.yaytris.util;
+package eu.midnightdust.yaytris.util.sound;
 
 import eu.midnightdust.yaytris.Settings;
 
@@ -55,7 +55,7 @@ public class SoundUtil {
         }
     }
 
-    private static URL getResource(String fileLocation) {
+    protected static URL getResource(String fileLocation) {
         return SoundUtil.class.getResource(fileLocation);
     }
 
@@ -66,80 +66,10 @@ public class SoundUtil {
      * @param line      the DataLine responsible for audio playback
      * @param volume    the requested volume in percent (0-100%)
      */
-    private static void setVolume(Line line, int volume) {
+    protected static void setVolume(Line line, int volume) {
         if (volume < 0 || volume > 100)
             throw new IllegalArgumentException("Volume not valid: " + volume);
         FloatControl gainControl = (FloatControl) line.getControl(FloatControl.Type.MASTER_GAIN);
         gainControl.setValue(20f * (float) Math.log10(volume/100f));
     }
-
-    /**
-     * Handle music in separate threads to not interrupt the main game
-     */
-    public static class MusicThread extends Thread {
-        private static final int BUFFER_SIZE = 8192;
-        private final boolean looped;
-        private final String fileLocation;
-        private boolean playing;
-
-        MusicThread(String fileLocation, boolean looped) {
-            this.fileLocation = fileLocation;
-            this.looped = looped;
-            this.playing = true;
-        }
-
-        public void stopMusic() {
-            this.playing = false;
-        }
-
-        @Override
-        public void run() {
-            do {playMusic(fileLocation);} while (looped && playing);
-        }
-
-        /**
-         * INTERNAL!
-         * Play the long audio file found at the specified location.
-         * Fades out after calling {@link #stopMusic()}.
-         * Adapted from: <a href="https://www.baeldung.com/java-play-sound">Baeldung</a>
-         * @see SoundUtil#playMusic(String, boolean)
-         */
-        private void playMusic(String fileLocation) {
-            try (AudioInputStream stream = AudioSystem.getAudioInputStream(getResource(fileLocation))) {
-                AudioFormat format = stream.getFormat();
-                DataLine.Info info = new DataLine.Info(SourceDataLine.class, format);
-
-                SourceDataLine sourceDataLine = (SourceDataLine) AudioSystem.getLine(info);
-                sourceDataLine.open(format);
-                sourceDataLine.start();
-                setVolume(sourceDataLine, Settings.musicVolume);
-                float fadeOut = 1.0f;
-
-                byte[] bufferBytes = new byte[BUFFER_SIZE];
-                int readBytes;
-                while ((readBytes = stream.read(bufferBytes)) != -1) {
-                    if (!playing) {
-                        fadeOut = (float) Math.sin(fadeOut-0.01f); // Sinus fade-out
-                        setVolume(sourceDataLine, (int) (fadeOut * Settings.musicVolume));
-                        if (fadeOut <= 0) break;
-                    }
-                    sourceDataLine.write(bufferBytes, 0, readBytes);
-                }
-
-                sourceDataLine.drain();
-                sourceDataLine.close();
-            } catch (LineUnavailableException | IOException | UnsupportedAudioFileException e) {
-                throw new RuntimeException(e);
-            }
-        }
-    }
-
-    public static class LineUpdateListener implements LineListener {
-        @Override
-        public void update(LineEvent event) {
-            if (LineEvent.Type.STOP == event.getType()) {
-                event.getLine().close();
-            }
-        }
-    }
 }