changes on Interface 4.

src/main/java/device/Device.java

@@ -7,6 +7,7 @@ public interface Device {
 	int getVolume();
 	void next();
 	void prev();
+	String play();
 	//get deviceName, Album and current Item
 	String getInfoText();
 	//get a list of public methods
@@ -15,6 +16,8 @@ public interface Device {
 	String chooseItem(int itemNr);
 	// get the actual album
 	String[] getItemList();
-	String play();
-
+	//mute the Volume and returns an Info.
+	String mute();
+	//unmute the Volume and returns an Info.
+	String unmute();
 	}

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

@@ -90,6 +90,16 @@ public class CDPlayer implements Device {
         return loadedCD.getPlayList();
     }
 
+    @Override
+    public String mute() {
+        return null;
+    }
+
+    @Override
+    public String unmute() {
+        return null;
+    }
+
     @Override
     public String play() {
         if(isCdFlapOpen()){

src/main/java/device/radioPlayer/RadioPlayer.java

@@ -166,6 +166,16 @@ public class RadioPlayer implements Device {
         return null;
     }
 
+    @Override
+    public String mute() {
+        return null;
+    }
+
+    @Override
+    public String unmute() {
+        return null;
+    }
+
 
     @Override
     public String play() {

src/main/java/device/usbPlayer/UsbPlayer.java

@@ -160,6 +160,16 @@ public class UsbPlayer implements Device {
         return null;
     }
 
+    @Override
+    public String mute() {
+        return null;
+    }
+
+    @Override
+    public String unmute() {
+        return null;
+    }
+
 
     @Override
     public String play() {