Question

This is a follow-up to this question.

The question is on the second line below.

"".split("x");   //returns {""}   // ok
"x".split("x");  //returns {}   but shouldn't it return {""} because it's the string before "x" ?
"xa".split("x"); //returns {"", "a"}    // see?, here "" is the first string returned
"ax".split("x"); //returns {"a"}

Answer 1

As per the java.util.regex.Pattern source, which String.split(..) uses,

"".split("x");   // returns {""} - valid - when no match is found, return the original string
"x".split("x");  // returns {} - valid - trailing empty strings are removed from the resultant array {"", ""}
"xa".split("x"); // returns {"", "a"} - valid - only trailing empty strings are removed
"ax".split("x"); // returns {"a"} - valid - trailing empty strings are removed from the resultant array {"a", ""}