String method to get unknown value that matches regex from string

Question

Hi,

In Java is there a way to extract the value of an unknown subset of a string via a regex. For example in the following string "hello world 1234" I want to be able to extract the value 1234 via the regex [0-9]*. Is there a way to do this?

Answer 1

Yes - put the bit that you want into a group in the regex.

There's a sort of tutorial here or find "capturing the string that matched a pattern" in this longer page.

Answer 2

It's actually quite easy with provided API:

• you generate your regexp pattern by Pattern p = Pattern.compiler("regexp")
• you try to match the pattern with the string you need: Matcher m = p.matches(string)

• lastly you iterate over groups captured

  for (int i = 0; i < m.groupCount(); ++i) System.out.println(m.group(i));

Answer 3

Additionally, you can always check the 'official' tutorial regarding REGEX: here.