Inserting a newline into a string

[sleeper0110]

Problem: I need to insert a newline into a string where a letter follows a non-letter.
Example String: A63B432

I want to insert a newline after A63

I only have the string class available to me.
I'm familiar with regular expressions however I don't know how to use the String class to insert a newline.

I'm guessing the regular expression I'm looking for would be similar to:
[\.0-9_][a-zA-Z]
(for . OR didgit OR underscore followed by an alpha character)

But how to insert a newline between the two?

Any ideas?
Thanks.

[gimbal2]

Check out the different methods of the Pattern and Matcher classes (which are to do with regular expressions) and you may just get an idea yourself.

Matcher (Java Platform SE 7 )

[sleeper0110]

Thanks, but as I've said in my original posting, I only have access to the String class.
I can't use Matcher or Pattern.

Anybody have ideas on how to do this with only the String class?

[Norm]

The String class has methods for accessing its characters. See the API doc.

How will you determine if a char in the String is a letter or not?

[sleeper0110]

I was hoping I could use either [\.0-9_] or \W in the regular expression to represent a non letter character.

[Norm]

Is this a regular expression question?

[sleeper0110]

I got it working using this:

System.out.println(Str.replaceAll("([\\.0-9_])([a-zA-Z])", "$1\n$2" ));
which will insert a newline character in between a non-letter followed by a letter.