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 them and for each of those pairs, iterates over the target string, looks for the from using indexOf(), and replaces it with the value of to. It does all the work on a StringBuffer and eventually returns a String.

I replaced that code with this line: replaceAll("[,. ]*", "");
And I ran some comparative performance tests.
When comparing for 1,000,000 iterations, I got this:

Old Code: 1287ms
New Code: 4605ms

3 times longer!

I then tried replacing it with 3 calls to replace:
replace(",", "");
replace(".", "");
replace(" ", "");

This resulted with the following results:

Old Code: 1295
New Code: 3524

2 times longer!

Any idea why replace and replaceAll are so inefficient? Can I do something to make it faster?

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Edit: Thanks for all the answers - the main problem was indeed that [,. ]* did not do what I wanted it to do. Changing it to be [,. ]+ almost equaled the performance of the non-Regex based solution. Using a pre-compiled regex helped, but was marginal. (It is a solution very applicable for my problem.

Test code:
Replace string with Regex: [,. ]*
Replace string with Regex: [,. ]+
Replace string with Regex: [,. ]+ and Pre-Compiled Pattern

Answer 1

While using regular expressions imparts some performance impact, it should not be as terrible.

Note that using String.replaceAll() will compile the regular expression each time you call it.

You can avoid that by explicitly using a Pattern object:

Pattern p = Pattern.compile("[,. ]+");  // repeat only the following part: String output = p.matcher(input).replaceAll(""); 

Note also that using + instead of * avoids replacing empty strings and therefore might also speed up the process.