Java正则表达式找不到我的Char类

Question

Very simply, idParser as seen below is not finding the number in my passedUrl string. Here is the LogCat out for the Lod.d's:

01-05 11:27:48.532: D/WEBVIEW_REGEX(29447): Parsing: http://mymobisite.com/cat.php?id=33
01-05 11:27:48.532: D/WEBVIEW_REGEX(29447): idParse: No Matches Found.

annnnd heres the block of trouble.

Log.d("WEBVIEW_REGEX", "Parsing: "+passableUrl.toString());
Matcher idParser = Pattern.compile("[0-9]{5}|[0-9]{4}|[0-9]{3}|[0-9]{2}|[0-9]{1}").matcher(passableUrl);
if(idParser.groupCount() > 0)
    Log.d("WEBVIEW_REGEX", "idParse: " + idParser.group());
else Log.d("WEBVIEW_REGEX", "idParse: No Matches Found.");

note, this is me getting a bit sloppy now, I've tried a bunch of different syntaxes (all verified working at http://www.regextester.com/index2.html on all three modes ) and I've even looked up the documentation ( http://docs.oracle.com/javase/tutorial/essential/regex/char_classes.html ). This is starting to get on my final nerve. using

.find()

instead of group() stuff just yields "false" ... Can someone help me to understand why i cant get this regular expression to work?

Cheers!

Answer 1

The problem is that groupCount() doesn't do what you think it does. You should instead use idParser.find() . Like this:

if(idParser.find())
    Log.d("WEBVIEW_REGEX", "idParse: " + idParser.group());
else Log.d("WEBVIEW_REGEX", "idParse: No Matches Found.");

You could also simplify the pattern a bit, using \\d{1,5} instead:

Matcher idParser = Pattern.compile("\\d{1,5}").matcher(passableUrl);

---

Full example:

String passableUrl = "http://mymobisite.com/cat.php?id=33";
Matcher idParser = Pattern.compile("\\d{1,5}").matcher(passableUrl);
if (idParser.find())
    System.out.println("idParse: " + idParser.group());
else 
    System.out.println("idParse: No Matches Found.");

Outputs:

idParse: 33

Answer 2

There are no ( ) braces hence zero groups.

All groups are numbered from left to right with a starting ( . Matcher.group(1) would be the first group. Matcher.group() is the entire match. You need find() to move to the first match. Others already indicated there are simpler patterns, like "\\\\d+$" , a string ending with at least one digit.