@Override
    public void mouseExited(final MouseEvent event) {
      // No highlighting if the mouse left the component.
      if (editedRegister == -1) {
        highlightedRegister = -1;
        repaint();
      }
    }
Tests whether a character is a valid hex input value.

@param c The character to test.
@return True, if the character is a valid hex input value. False, otherwise.
java/zylib/src/main/java/com/google/security/zynamics/zylib/gui/JRegisterView/JRegisterView.java