Google搜索结果的正则表达式在android中不起作用

Question

I try to scrape google search result with this code

 Pattern p = Pattern.compile("<h3.*?><a.*?href=\"(.*?)\".*?</h3>");
        Matcher m = p.matcher(html);

in android studio its work, but in android devices takes too much time ...

how can i fix that ?

Answer 1

This is due to your regex causing catastrophic backtracking.

Adding the first .*? to an atomic group will help. An atomic group prevents backtracking in that particular group.

(?><h3.*?>)<a.*?href=\"(.*?)\".*?<\/h3>

See https://regex101.com/r/hl2ARK/1 and try removing the first group to replicate your original regex.

Pretty much everything you need to know about catasrophic backtracking can be found here http://www.regular-expressions.info/catastrophic.html