clean code: extract inner classes

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);
+        }
+    }
+}