@Override
    public void focusGained(final FocusEvent event) {}
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