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.

Answer 1

Note that to parse HTML, you'd better use some dedicated parser (eg 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