Convert a python regexp to java

Question

I know it has already been asked Here however I would like to use named group in java like Pshemo suggested and I can't figure what's wrong with my regex conversion:

Here is the python regexp:

regexp = re.compile(r'(?P<delim>[^\w\n"\'])(?P<space> ?)(?P<quote>["\']).*?(?P=quote)(?P=delim)', re.DOTALL | re.MULTILINE)
matches = regexp.findall(content)

Here is my java converted regexp:

String regexp = "(?<delim>[^\\w\\n\\\"'])(?<space> ?)(?<quote>[\\\"']).*?(?=quote)(?=delim)";
Pattern pattern = Pattern.compile(regexp, Pattern.DOTALL | Pattern.MULTILINE);
Matcher matcher = pattern.matcher(content);

What I am doing wrong ?

What is the issue? Note you converted named backreferences into positive lookaheads ((?P=quote) => (?=quote)) — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Nov 22, 2016 at 11:38

Wiktor Stribiżew · Accepted Answer · 2016-11-22 11:45:21Z

1

You converted named backreferences into positive lookaheads ((?P=quote) => (?=quote)), while you need \k<groupname>:

String regex = "(?<delim>[^\\w\n\"'])(?<space> ?)(?<quote>[\"']).*?\\k<quote>\\k<delim>";

Tested at OCPSoft regex tester:

answered Nov 22, 2016 at 11:45

Wiktor Stribiżew

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2 Comments

banetl Over a year ago

Thank you, It seems to work way better than this way. It is supposed to catch the content of a line like "one", "two", "three", "four", "five". However I do not understand why it doesn't work if the spaces between the elements are removed: "one","two","three","four","five". The group spaces should match the space character 0 or 1 time, why isn't it matching when there are 0 spaces ?

Wiktor Stribiżew Over a year ago

You need to make the delim optional, (?<delim>[^\w\n"']?)(?<space> ?)(?<quote>["']).*?\k<quote>\k<delim> as the string starts with a quote.

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