A regular expressin problem: String.matches & the pair of Pattern & Matcher

Question

I observe this problem when working on pattern match for Z5Z-5Z5, Z5Z 5Z5 or Z5Z5Z5.
When I use the match method of the String class, the correct pattern will yield true with
!str.matches("^[A-Za-z]\\d[A-Za-z]\\s?|-?\\d[A-Za-z]\\d$").
When I use the pair classes of regex:
Pattern p = Pattern.compile("^[A-Za-z]\\d[A-Za-z]\\s?|-?\\d[A-Za-z]\\d$");
Matcher m = p.matcher(str);
a string of "v7u h4e" (two blank spaces in between) can pass the !m.find().
Have anyone else experienced the same situation?
Do I use them right, or bugs?
Thanks for your input.
v.

Answer 1

This is why I wish regex references would list the
operator precedence. What do you mean? My regex reference does show that right under the section called "Operators" in the second chapter.
Maybe you need to update your references and buy "Programming Perl"? :)
I think there are only three
levels of precedence, but it needs to be crystal clear
that | has the lowest precedence (even lower than
putting two tokens together!) and often needs
parentheses: "\w\d|\s\w" means "(\w\d)|(\s\w)", not
"\w(\d|\s)\w".Actually for that particular operator it is pretty consistent. It is always very low. Even when I was introduced to the theory of regex's in school the precedence was lower than everything else.