Replace string inside tags?

Question

I want to replace a content inside some tags, eg:

<p>this it to be replaced</p>

I could extract the content between with groups like this, but can i actually replace the group?

str = str.replaceAll("<p>([^<]*)</p>", "replacement");

dacwe · Accepted Answer · 2012-06-21 12:45:27Z

9

You can use lookaround (positive lookahead and lookbehind) for this:

Change the regex to: "(?<=<p>)(.*?)(?=</p>)" and you will be fine.

Example:

String str = "<p>this it to be replaced</p>";
System.out.println(str.replaceAll("(?<=<p>)(.*?)(?=</p>)", "replacement"));

Output:

<p>replacement</p>

Note however that if you are parsing HTML you should be using some kind of a HTML parser, often regular expressions is not good enough...

answered Jun 21, 2012 at 12:45

dacwe

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Bohemian · Accepted Answer · 2012-06-21 12:46:41Z

8

Change the regex to this:

(?<=<p>).*?(?=</p>)

ie

str = str.replaceAll("(?<=<p>).*?(?=</p>)", "replacement");

This uses a "look behind" and a "look ahead" to assert, but not capture, input before/after the matching (non-greedy) regex

Just in case anyone is wondering, this answer is different to dacwe's: His uses unnecessary brackets. This answer is the more elegant :)

answered Jun 21, 2012 at 12:46

Bohemian♦

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@dacwe They're totally unnecessary. You can use $0 (which is how you refer to the entire match) which in this case is equivalent to your $1 :)