I maybe miss something, but i'd like to know why this pattern is valid :
Pattern.compile("([0-9]{1,})");
The compile does not throw an exception despite that the occurence is not valid.
Thx a lot
1 Answer
despite that the occurence is not valid
quantifiers can be represented using {n,m} syntax where:
{n}- exactlyntimes{n,}- at leastntimes{n,m}- at leastnbut not more thanmtimes
Source: https://docs.oracle.com/javase/tutorial/essential/regex/quant.html
(notice that there is no {,m} quantifier representing "not more than m times") because we don't really need one, we can create it via {0,m})
So {1,} is valid and simply means "at least once".
To avoid confusion we can simplify it by replacing {1,} quantifier with more known form + like
Pattern.compile("([0-9]+)");
Most probably you also don't need to create capturing group 1 by surrounding [0-9]+ with parenthesis. We can access what regex matched with help of group 0, so such group 1 is redundant in most cases.
{x,}means at leastxtimes and{,x}means at mostxtimes.{,x}is not proper regex (at least in Java), we need explicit{0,x}for such case.