checking for ints in a String

[SteroidalPsycho]

I have a String of a telephone number in the format xxx xxx xxxx or xxx xxxx. Is there a way to use String's methods to make sure these are ints and white space only?

[iluxa]

for (int i = 0; i < str.length (); i ++) {
  char ch = str.charAt (i);
  if (ch != ' ' && (ch < '0' || ch > '9')) {
    //bad character
  }
}