Why this code would fail?
assertTrue(Pattern.matches("[^a-zA-Z0-9]", "abc;"));
views:
91answers:
5
+3
A:
Because the .matches() method tries to match the entire string, and your regex doesn't match the entire string, only the semicolon. The Matcher.find() method would work (in this case: find a character that is not a letter between a and z nor a number between 0 and 9. Of course, it will also find á, ö etc.)
What is it you really want to do?
Tim Pietzcker
2010-02-12 10:38:50
+1
A:
Because Pattern.matches() is equivalent to the corresponding pattern being compiled and fed to Matcher.matches() which, as specified, checks to see if the entire input matches the pattern. If you only want to match part of the input, you'll want to use Matcher.find() instead.
Amber
2010-02-12 10:40:22
I believe the OP is trying to match the `;` in the target string. So it's not the regex that's wrong, it's using `matches()` instead of `find()`, as others have pointed out. In any case, "try this instead" is not a particularly helpful answer.
Alan Moore
2010-02-12 11:04:52
A:
Because when you put the ^ inside, it means any char not in a-z or A-Z. What you want is ^[a-zA-Z0-9]
Valentin Rocher
2010-02-12 10:43:41
+2
A:
If fails because matches tries to match the complete string, your regexp matches 1 character which is not in the character ranges you list, if you change to:
assertTrue(Pattern.compile("[^a-zA-Z0-9]").matcher("abc;").find());
it should assert true.
rsp
2010-02-12 10:45:40
It will assert true, by matching the `";"`, but I suspect that is not what the OP had in mind.
finnw
2010-02-12 10:50:15
Yes, that's what I mean. What about if I use Pattern.matches(".*[^a-zA-Z0-9].*", "abc;")? Is it the same?
jackysee
2010-02-12 10:57:23
@jackysee, It would result in the same behaviour, the difference is that between finding a non-alphanumeric and checking that a string has the format "anything" "non-alphanumeric" "anything" which is not quite the same. Using the find, you could look for the next non-alpha character in your string, using matches you cannot do that for instance.
rsp
2010-02-12 11:42:03