Faster alternatives to replace method in a Java String?

Question

The fact that the replace method returns a string object rather than replacing the contents of a given string is a little obtuse (but understandable when you know that strings are immutable in Java). I am taking a major performance hit by using a deeply nested replace in some code. Is there something I can replace it with that would make it faster?

Answer 1

This is what StringBuilder is meant for. If you're going to be doing a lot of manipulation, do it on a StringBuilder, then turn that into a String whenever you need to.

StringBuilder is described thus:

"A mutable sequence of characters. This class provides an API compatible with StringBuffer, but with no guarantee of synchronization".

It has replace (and append, insert, delete, et al) and you can use toString to morph it into a real String.

Answer 2

The previous posts are right, StringBuilder/StringBuffer are a solution.

But, you also have to question if it is a good idea to do the replace on big Strings in memory.

I often have String manipulations that are implemented as a stream, so instead of replacing it in the string and then sending it to an OutputStream, I do the replace at the moment that I send the String to the outputstream. That works much faster than any replace.

This works much faster if you want this replace to implement a template mechanism. Streaming is always faster since you consume less memory and if the clients is slow, you only need to generate at a slow pace - so it scales much better.