Not sure how string split actually works in this case

Question

I don't get the following:

In the following String:

String s = "1234;x;;y;";

if I do:
String[] s2 = s.split(";");

I get s2.length to be 4 and

s2[0] = "1234";  
s2[1] = "x";  
s2[2] = "";  
s2[3] = "y"; 

But in the string: String s = "1234;x;y;;";

I get:

s2.length to be 3 and

s2[0] = "1234";  
s2[1] = "x";  
s2[2] = "y"; 

?

What is the difference and I don't get 4 in the latter case as well?

UPDATE:
Using -1 is not was I was expecting as behavior.
I mean the last semicolon is the end of the String so in the latter example I was also expecting 4 as length of the array

Answer 1

From the docs,

This method works as if by invoking the two-argument split method with the given expression and a limit argument of zero. Trailing empty strings are therefore not included in the resulting array.

UPDATE:

You have five substrings separated by ; In the second case, these are 1234, x, y, and . As per the docs, all empty substrings (at the end) which result from the split operation would be eliminated. For details, look here.

If n is zero then the pattern will be applied as many times as possible, the array can have any length, and trailing empty strings will be discarded.

The string boo:and:foo, for example, yields the following results with these parameters:

Regex   Limit   Result
  :       2     { "boo", "and:foo" }
  :       5     { "boo", "and", "foo" }
  :      -2     { "boo", "and", "foo" }
  o       5     { "b", "", ":and:f", "", "" }
  o      -2     { "b", "", ":and:f", "", "" }
  o       0     { "b", "", ":and:f" }   // all the empty substrings at the end were eliminated