public class IsoTest {
    public static void main(String[] args) throws UnsupportedEncodingException {
        String iso = "ř";
        String notIso = "Ŧ";

        String charset = "ISO-8859-2";
        test(iso, charset);
        test(notIso, charset);
    }

    private static void test(String value, String charset) throws UnsupportedEncodingException {
        if(value.equals(new String(value.getBytes(charset), charset))){
            System.out.println(value + " belongs to " + charset);
        }else {
            System.out.println(value + " does not belong to " + charset);
        }
    }
}