The string is, for example "r1" and I need the 1 in an int form
Scanner sc = new Scanner("r1");
int result = sc.nextInt(); // should be 1
compiles correctly but has a runtime error, should I be using the delimiter? Im unsure what the delimiter does.
Well, there's a few options. Since you literally want to skip the "r" then read the number, you could use Scanner#skip. For example, to skip all non-digits then read the number:
Scanner sc = new Scanner("r1");
sc.skip("[^0-9]*");
int n = sc.nextInt();
That will also work if there are no leading non-digits.
Another option is to use non-digits as delimiters, as you mentioned. For example:
Scanner sc = new Scanner("x1 r2kk3 4 x56y 7g");
sc.useDelimiter("[^0-9]+"); // note we use + not *
while (sc.hasNextInt())
System.out.println(sc.nextInt());
Outputs the six numbers: 1, 2, 3, 4, 56, 7.
And yet another option, depending on the nature of your input, is to pre-process the string by replacing all non-digits with whitespace ahead of time, then using a scanner in its default configuration, e.g.:
String input = "r1";
input = input.replaceAll("[^0-9]+", " ");
And, of course, you could always just pre-process the string to remove the first character if you know it's in that form, then use the scanner (or just Integer#parseInt):
String input = "r1";
input = input.substring(1);
What you do depends on what's most appropriate for your input. Replace "non-digit" with whatever it is exactly that you want to skip.
By the way I believe a light scolding is in order for this:
Im unsure what the delimiter does.
The documentation for Scanner explains this quite clearly in the intro text, and even shows an example.
Additionally, the definition of the word "delimiter" itself is readily available.
