Question

Why does

int a = 1234;
String b = a + "";
String[] c = b.split("");

Result in:

c[0] = ""
c[1] = "1"
c[2] = "2"
c[3] = "3"
c[4] = "4"

Answer 1

String.split takes a regular expression String as an argument. You have provided an empty regex, which matches the empty string. Thus, you get one empty string match from the start of the string and then every character split by an empty string. You should probably provide a valid regex.

---

Ordinarily there would be an empty string at the end of the split, but Java intentionally excludes this from the array resulting from .split with this one-argument usage.

$ php -r "var_dump(preg_split('//', 1234));"
array(6) {
  [0]=>
  string(0) ""
  [1]=>
  string(1) "1"
  [2]=>
  string(1) "2"
  [3]=>
  string(1) "3"
  [4]=>
  string(1) "4"
  [5]=>
  string(0) ""
}