Number input = null;
try {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
NumberFormat nf = NumberFormat.getInstance();
while (true) {
System.out.println("Enter a number (-1 to quit): ");
String s = br.readLine();
try {
input = nf.parse(s);
}
catch (ParseException ex) {
System.out.println(s + " is not a number I understand.");
continue;
}
double d = input.doubleValue();
if (d < 0) break;
double root = Math.sqrt(d);
System.out.println("The square root of " + s + " is " + root);
}
}
catch (IOException ex) {System.err.println(ex);}
