java - Regex to remove spaces between numbers only

Question

I need to remove the spaces between numbers only, so that a string like this:

"Hello 111 222 333 World!"

becomes

"Hello 111222333 World!"

I've tried this:

message = message.replaceAll("[\d+](\s+)[\d+]", "");

Doesn't seem to get it done.

Answer 1

You can use this lookaround based regex:

 String repl = "Hello 111 222 333 World!".replaceAll("(?<=\d) +(?=\d)", "");
 //=> Hello 111222333 World!

This regex "(?<=\d) +(?=\d)" makes sure to match space that are preceded and followed by a digit.