Code Answer: replacing regex in java string

I have this java string:

String bla = "<my:string>invalid_content</my:string>";

How can I replace the "invalid_content" piece?

I know I should use something like this:

bla.replaceAll(regex,"new_content");

in order to have:

"<my:string>new_content</my:string>";

but I can't discover how to create the correct regex

help please :)

From stackoverflow

You could do something like

String ResultString = subjectString.replaceAll("(<my:string>)(.*)(</my:string>)", "$1whatever$3");

The PCRE would be:
```
/invalid_content/
```
For a simple substitution. What more do you want?

Alan Moore : A solution that works in Java, maybe? Besides, I think the surrounding XML tags are needed to identify the invalid content, and that's what the OP was having trouble with.
Is invalid_content a fix value? If so you could simply replace that with your new content using:
```
bla = bla.replaceAll("invalid_content","new_content");
```
Mark's answer will work, but can be improved with two simple changes:
- The central parentheses are redundant if you're not using that group.
- Making it non-greedy will help if you have multiple my:string tags to match.
Giving:
```
String ResultString = SubjectString.replaceAll
    ( "(<my:string>).*?(</my:string>)" , "$1whatever$2" );
```
But that's still not how I'd write it - the replacement can be simplified using lookbehind and lookahead, and you can avoid repeating the tag name, like this:
```
String ResultString = SubjectString.replaceAll
    ( "(?<=<(my:string)>).*?(?=</\1>)" , "whatever" );
```
Of course, this latter one may not be as friendly to those who don't yet know regex - it is however more maintainable/flexible, so worth using if you might need to match more than just my:string tags.

DroidIn.net : Great answer - I think this should be marked as accepted solution
See Java regex tutorial and check out character classes and capturing groups.

Code Answer