Dokud není z klávesnice načtena požadovaná hodnota:
String vstup = ""; float number; boolean isOK; // create a reader from standard input BufferedReader in = new BufferReader(new InputStream(System.in)); // until a valid number is given, try to read it do { String input = in.readLine(); try { number = Float.parseFloat(input); isOK = true; } catch (NumberFormatException nfe) { isOK = false; } } while(!isOK); System.out.println("We've got the number " + number);