Add constant when replaceAll by regex

Question

I have a regex for exclude non digit symbols:

\\D

And i need to replace all non digit symbols to spaces:

"145632afaf214+--)(".replaceAll("\\D", ""); // 145632214

Can I add to result some constant at the beginning string if i have result from the regex? I would see result like this:

"145632afaf214+--)(".replaceAll(improvedRegex, ""); // CONST145632214

However:

"qwqtyafaf+--)(".replaceAll(improvedRegex, ""); // ""

EDIT: This regex adds CONST to the string but doesn't filter digits:

replaceAll("(^.+)", "CONST$1")