What is a word boundary in regex, does  match hyphen '-'?

Question

I'm trying to use regexes to match space-separated numbers. I can't find a precise definition of ("word boundary"). I had assumed that -12 would be an "integer word" (matched by -?d+) but it appears that this does not work. I'd be grateful to know of ways of .

[I am using Java regexes in Java 1.6]

Example:

Pattern pattern = Pattern.compile("\s*\b\-?\d+\s*");
String plus = " 12 ";
System.out.println(""+pattern.matcher(plus).matches());

String minus = " -12 ";
System.out.println(""+pattern.matcher(minus).matches());

pattern = Pattern.compile("\s*\-?\d+\s*");
System.out.println(""+pattern.matcher(minus).matches());

This returns:

true
false
true

question from:https://stackoverflow.com/questions/65846830/tweaking-regex-match

Answer 1

A word boundary, in most regex dialects, is a position between w and W (non-word char), or at the beginning or end of a string if it begins or ends (respectively) with a word character ([0-9A-Za-z_]).

So, in the string "-12", it would match before the 1 or after the 2. The dash is not a word character.