Java Regex Metacharacters

Question

I found this thread and one of users on it posted the following line of code:

String[] digits2 = number.split("(?<=.)");

I have consulted a couple of sources- like 1 and 2 -to decipher what this code mean but I can't figure it out. Can anybody explain what the argument in the split() method means?

Edit : To anyone who has the same question as I had, here's another helpful link

Answer 1

This is a positive lookbehind . The overall expression means "after any character, but without capturing anything". Essentially, if the string looks like

ABC

then the matches would occur at | , between the characters.

A|B|C|

Answer 2

.split("") (on an empty string/pattern) will match the empty string at the start of the regex. This is an additional empty string character that is undesirable. (?<=.) is a zero-width assertion (does not consume any characters) that matches the zero-width space followed by any character (followed by because it is a lookbehind). This splits on the empty string between each character, but not the empty space between the first character and the start of the string.