Regex not matching empty string

Question

Pattern srcAttrPattern = Pattern.compile("(?i)(?<=src=\")[^\"]*(?<!\")");
Matcher srcMatcher=srcAttrPattern.matcher("src=\"\"");
System.out.println(srcMatcher.find());

This prints false. How do I interpret the above code ? Is there any modification needed to include src="" for the above code to serve purpose of empty as well as filled string. This statement is basically to match the src tag in <img> of html contents.

You can remove the last assertion, but doesn't guarantee a dbl quote at the end, change it to (?="). But why go to all the trouble with a slow as paint dry assertions.. Use something more reasonable, src="(.*?)" — user557597
– user557597, Commented Mar 18, 2016 at 21:42

Wiktor Stribiżew · Accepted Answer · 2016-03-18 21:03:44Z

2

Note that to parse HTML, you'd better use some dedicated parser (e.g. Jsoup).

As for the current issue of matching a src="" string, the final negative lookbehind requires the character before the current location to be other than a quote. Since you are using a negated character class [^"]* (0+ characters other than ") you just do not need that lookbehind.

Remove (?<!") and you will match the empty string in src="" with the "(?i)(?<=src=\")[^\"]*".

See the regex demo

answered Mar 18, 2016 at 21:03

Wiktor Stribiżew

631k41 gold badges502 silver badges632 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Regex not matching empty string

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related