Question about split()

[Katrin Perry]

Hi,

Would anyone be able to explain me why in this code:

String s = "aaaaaaaaabbb";
String[] arr = s.split("a{3}");
System.out.println(arr.length + "");

The output is 4, rather than 3

Thanks
Katrin

[Jesper de Jong]

The split() method splits the string around occurrences of the regular expression that you pass to it. Your regular expression "a{3}" matches the character a, tree times (so: "aaa"). Did you look at the elements in the returned array? It contains: three times the empty string, and the fourth element contains "bbb".

Note that split() removes the matches from the input string and returns the text between the matches. So the "aaa"'s are removed, and the text around those "aaa"'s is returned. Since there are no characters between the nine "a"'s, you'll get three times the empty string first, and then the final "bbb".

Lookup the API documentation of the String.split() method for an exact description of what the method does.

[Katrin Perry]

Thank you Jesper.

In general I understand how it works, I suppose I got a bit confused about the first empty String in the returned array. I understand about where the other 2 would come from + the "bb"

Katrin

[Burkhard Hassel]

Howdy!

I modified Katrin's code a bit, original in bold:

public static void main(String[] args) {
[B]String s = "aaaaaaaaabbb";
String[] arr = s.split("a{3}");
System.out.println(arr.length + "");[/B]
System.out.println(s);
System.out.println("..X..X..X..X");
for(String ele: arr){
System.out.print  ("<");
System.out.print  (ele);
System.out.println(">");
}
}
 
[I]prints out:[/I]
4
aaaaaaaaabbb
..X..X..X..X
<>
<>
<>
<bbb>

The first three are the three null-strings after the triple-a.
The split splits just after the positions marked by the X.


Hope it helps,

Yours,
Bu.

edit: the last C is just one too many...
[ September 13, 2007: Message edited by: Burkhard Hassel ]