No, you can't do that with regex. Regex has no notion of numeric values, so doing arithmetic with numbers is not possible (assuming you wanted to convert "12 54 1 65" into "36 162 3 195").
Note that with some languages and regex implementations you can do this (Perl as Chris posted), but this is not a regex thing, and especially not a Java-regex thing.
You said you have already resolved the issue, so I guess you went the "manual" way, converting each match into an integer and multiplying that with 3.
