Production-Code for CDPlayer-Method [Quieter] produced.

src/main/java/device/cdPlayer/CDPlayer.java

@@ -21,12 +21,20 @@ public class CDPlayer implements Device {
 
     @Override
     public void louder() {
-
+        if(volume < 100) {
+            volume += 1;
+        } else {
+            volume = 100;
+        }
     }
 
     @Override
     public void quieter() {
-
+        if(volume > 0) {
+            volume -= 1;
+        } else {
+            volume = 0;
+        }
     }
 
     @Override