Question

I am trying to use Regular Expressions to decode some HTML I retrieve from a webpage.
I want to transform some <iframe> tags into links.

The code I’m using should be working fine according to me and some testprograms, however when I run it on my android device it does not find any matches (where as in the test programs it does).

The regular expression I am using is as follows (keep in mind I’m coding in Java, so I need to escape the escape character as well):

String regularExpression = "<iframe.+?src=\\\\?(\\S+).+?(><\\\\?/iframe>|\\\\?/>)";
String replacement = "<a href=$1>Youtube</a>";

input.replaceAll(regularExpression, replacement);

From what I can gather from this it should replace all <iframe> tags that have a src attribute to hyperlinks with that source. However when I feed the following input to it, it does nothing with it:

<iframe src=\"http:\/\/www.youtube.com\/embed\/s6b33PTbGxk\" frameborder=\"0\" width=\"500\" height=\"284\"><\/iframe>

The response is simply the exact same text, only with the escape-characters removed:

<iframe src="http://www.youtube.com/embed/s6b33PTbGxk" frameborder="0" width="500" height="284"></iframe>

Can someone help me and explain what I’m doing wrong? I only started learning Regular Expressions yesterday, but I just can’t for the life of me figure out why this doesn’t work.

Answer 1

The method String.replaceAll doesn’t modify the string. It can’t because strings are immutable. Instead it returns a new string with the result. You need to assign this result to something:

String result = input.replaceAll(regularExpression, replacement);

Also, don’t use regular expressions to parse HTML.