String.replaceAll is considerably slower than doing the job yourself

Question

I have an old piece of code that performs find and replace of tokens within a string.

It receives a map of from and to pairs, iterates over

Answer 1

As I have put in a comment [,. ]* matches the empty String "". So, every "space" between characters matches the pattern. It is only noted in performance because you are replacing a lot of "" by "".

Try doing this:

Pattern p = Pattern.compile("[,. ]*");
System.out.println(p.matcher("Hello World").replaceAll("$$$");

It returns:

H$$$e$$$l$$$o$$$$$$W$$$o$$$r$$$l$$$d$$$!$$$

No wonder it is slower that doing it "by hand"! You should try with [,. ]+