diff -r f7433671fec5 -r 1c62c6009161 src/main/java/de/uapcore/sudoku/SudokuTextField.java
--- a/src/main/java/de/uapcore/sudoku/SudokuTextField.java	Sat Jul 25 15:56:48 2020 +0200
+++ b/src/main/java/de/uapcore/sudoku/SudokuTextField.java	Mon Jul 27 10:56:17 2020 +0200
@@ -114,7 +114,7 @@
         if (getText().isEmpty()) {
             return 0;
         } else {
-            return Integer.valueOf(getText());
+            return Integer.parseInt(getText());
         }
     }
 
@@ -122,6 +122,7 @@
      * Sets the field's value.
      *
      * @param v the number from 1 to 9 or zero to clear the field
+     * @throws IllegalArgumentException if v is not between 0 and 9
      */
     public void setValue(int v) {
         if (v == 0) {