Regex to find an integer within a string

Question

I\'d like to use regex with Java.

What I want to do is find the first integer in a string.

Example:

String = \"the 14 dogs ate 12 bones\"
         


        

Answer 1

In addition to what PiPeep said, if you are trying to match integers within an expression, so that 1 + 2 - 3 will only match 1, 2, and 3, rather than 1, + 2 and - 3, you actually need to use a lookbehind statement, and the part you want will actually be returned by Matcher.group(2) rather than just Matcher.group().

unescaped: ([0-9])?((?(1)(?:[\+-]?\d+)|)(?:[eE][\+-]?\d+)?)
  escaped: ([0-9])?((?(1)(?:[\\+-]?\\d+)|)(?:[eE][\\+-]?\\d+)?)

Also, for things like someNumber - 3, where someNumber is a variable name or something like that, you can use

unescaped: (\w)?((?(1)(?:[\+-]?\d+)|)(?:[eE][\+-]?\d+)?)
  escaped: (\\w)?((?(1)(?:[\\+-]?\\d+)|)(?:[eE][\\+-]?\\d+)?)

Although of course that wont work if you are parsing a string like The net change to blahblah was +4