string.replaceAll（）性能是否受到字符串不变性的影响？

Question

Lets say I called replaceAll() on a big string that replaced 1,000 matching instances. Does it mean that 1,000 strings were created and reassigned in process because of string immutability? Is there any faster alternatives?

Answer 1

If you dig into String , you'll see that it delegates replaceAll() to Pattern & Matcher and Matcher.replaceAll() uses a StringBuilder to store the eventually returned value.

So no, String.replaceAll() does not create more than a small number of objects.

Answer 2

you can try with a StringBuffer / StringBuilder , since they are mutable CharSequence s:

CharSequence veryBigString = new StringBuilder();
Pattern.compile(regex).matcher(veryBigString).replaceAll(replacement);