Re: Regex: Capturing and replacing question

Lew wrote:

Hal Vaughan wrote:
I'm using regexes to find any place in a string where there is a small
letter followed by a capital one and put a space between them. I'm
using "([a-z])([A-Z])" as the pattern to search for and using "$1 $2" as
the replacement string. This is working well in all my tests, but
since I
didn't find it documented where I'd feel safe,

From <http://java.sun.com/javase/6/docs/api/java/util/regex/Pattern.html>
Groups and capturing

Capturing groups are numbered by counting their opening parentheses from
left to right. In the expression ((A)(B(C))), for example, there are four
such groups:

1 ((A)(B(C)))
2 (A)
3 (B(C))
4 (C)

Group zero always stands for the entire expression.

Hal Vaughan wrote:
Is it correct that $1 in a replacement string references the first
captured
text sequence in the regex? And so on with $2, $3....?

Joshua Cranmer wrote:
The Matcher.appendReplacement says that $1 should be the output of
group(1), so that is correct.


<http://java.sun.com/javase/6/docs/api/java/util/regex/Matcher.html#appendReplacement(java.lang.StringBuffer
%20java.lang.String)>

The documentation is in the Javadocs for the relevant classes. Javadocs
are
often a great first place to look. The Javadocs are a place where you
will "find it documented" and should be "where [you]'d feel safe" to trust
it.

I goofed on that. I read all the info for Pattern, since that had all the
regex expressions and patterns, then went over the documentation at the
start of Matcher, but I didn't expect to find something like this explained
in the description of a particular method. I also had Googled quite a bit,
but had a high noise-to-signal ratio and kept getting sections that gave
the same general regex explanations. I would think that something like
this should have been in the main part of Pattern or Matcher and not in a
method description.

Hal

.

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