Java String.indexOf and empty Strings

Question

I\'m curious why the String.indexOf is returning a 0 (instead of -1) when asking for the index of an empty string within a string.

The Javadocs only say this method

Answer 1

int number_of_empty_strings_in_string_named_text = text.length() + 1

All characters are separated by an empty String. Additionally empty String is present at the beginning and at the end.