String.split vs StringUtils.split in Java gives different results

Question

Consider a string like below with delimiter __|__.

String str = "a_b__|__c_d";

str.split("__\\|__") gives 2 splits a_b and c_d StringUtils.split(str, "__|__") or StringUtils.split(str, "__\\|__") gives 4 splits a, b, c, d which is not desired.

Is there any way to make StringUtils.split() to give same results String.split()?

Answer 1

String.split() has some very surprising semantics, and it's rarely what you want. You should prefer StringUtils (or Guava's Splitter, discussed in the previous link).

Your specific issue is that String.split() takes a regular expression, while StringUtils.split() uses each character as a separate token. You should use StringUtils.splitByWholeSeparator() to split on the contents of the full string.

StringUtils.splitByWholeSeparator(str, "__|__");

Answer 2

No, as per documentation, second parameter of StringUtils.split is the list of all characters that are considered splitters. There is a different function in Apache Commons which does what you want - StringUtils.splitByWholeSeparator. Still, I don't get what's wrong with simple String.split.