Test Mnemonic, simplify class

refs #53

src/main/java/eva2/gui/Mnemonic.java

@@ -5,30 +5,26 @@ package eva2.gui;
  */
 class Mnemonic {
 
-    private char mnemonic;
-    private String text;
+    private final char mnemonic;
+    private final String text;
 
     /**
      *
      */
     public Mnemonic(String s) {
-        setString(s);
-    }
-
-    /**
-     *
-     */
-    public void setString(String s) {
         StringBuilder buf = new StringBuilder(s);
+        char c = Character.MIN_VALUE;
+
         for (int i = 0; i < buf.length(); i++) {
             if (buf.charAt(i) == '&') {
                 buf.deleteCharAt(i);
                 i++;
                 if (i < buf.length() && buf.charAt(i) != '&') {
-                    mnemonic = buf.charAt(i - 1);
+                    c = buf.charAt(i - 1);
                 }
             }
         }
+        mnemonic = c;
         text = buf.toString();
     }