Add displayMessage() method to Gui

schach/src/main/java/de/hs_mannheim/informatik/chess/gui/Gui.java

@@ -10,6 +10,7 @@ import java.awt.Insets;
 
 import javax.swing.JFrame;
 import javax.swing.JLabel;
+import javax.swing.JOptionPane;
 import javax.swing.JPanel;
 import javax.swing.SwingConstants;
 
@@ -118,4 +119,8 @@ public class Gui {
         }
     }
 	
+	public void displayMessage(String msg) {
+        JOptionPane.showMessageDialog(null, msg);
+    }
+	
 }