split() method

[Chandra Bhatt]

package string;
 
public class TrySplit {
    
    /** Creates a new instance of TrySplit */
    public TrySplit() {
    }
 
    public static void main(String... args) {
        String str = "scjpsmart";
        
        String[] tokens = str.split("");
        for(String s:tokens){
            System.out.println(">"+s+"<");
        }
        System.out.println(tokens.length);
    }
}
 

size of the array is returned "10", whereas it should have been 9.
Anyway if we say it is because of blank string "", then it should be 11;
staring and ending!!!
What is the matter here?

Please help!


Thanks,
cmbhatt
[ April 24, 2007: Message edited by: Barry Gaunt ]

[fred rosenberger]

From the API for split():

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.

[m ali]

hey its count is 10, including the starting and ending... doesn't it?

Thanks.

[Chandra Bhatt]

Well Fred,

It means, if we don't pass the second argument (limit), 0 is
used internally.

String s = "scjpsmart";
String[] tokens = s.split("",s.length()+1);

It should result 11 but doesn't give.

Why length+2 gives 11 (as exptected)

String s = "scjpsmart";
String[] tokens = s.split("",s.length()+2);

What does split() does if limit is negative?



Thanks,
cmbhatt

[Meena R. Krishnan]

..checking the API and this is what I found:

The limit parameter controls the number of times the pattern is applied and therefore affects the length of the resulting array. If the limit n is greater than zero then the pattern will be applied at most n - 1 times, the array's length will be no greater than n, and the array's last entry will contain all input beyond the last matched delimiter. If n is non-positive then the pattern will be applied as many times as possible and the array can have any length. 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.

..still trying to figure out how it works.

[Henry Wong]

This is all documented in the JavaDocs for the split() method.

[Quote deleted -- as already quoted]


In fact, the JavaDoc even follows this up with plenty of examples...

As a side note, I am generally one of those people who never get burned by something more than once (ie. I always learn from my mistakes). One of the few exceptions is the split() method. For some reason, I keep forgetting that the split() method, by default, will truncate trailing zero length matches.

Henry
[ April 24, 2007: Message edited by: Henry Wong ]

[Meena R. Krishnan]

Here is an eg. for all three cases applied to the same string

 
public static void main(String... args) {
String str = "abcdabcdabcdaa";

String[] tokens = str.split("a",-2);
for(String s:tokens){
         System.out.println(">"+s+"<");      //space,bcd,bcd,bcd,space,space
}
System.out.println(tokens.length);



System.out.println("0 limit");
tokens = str.split("a");
for(String s:tokens){
System.out.println(">"+s+"<");//space,bcd,bcd,bcd
}
System.out.println(tokens.length);

System.out.println("+ve limit");
tokens = str.split("a",6);
for(String s:tokens){
System.out.println(">"+s+"<");  //space,bcd,bcd,bcd,space,space
}
System.out.println(tokens.length);
}

and here is the o/p:

><
>bcd<
>bcd<
>bcd<
><
><
6
0 limit
><
>bcd<
>bcd<
>bcd<
4
+ve limit
><
>bcd<
>bcd<
>bcd<
><
><
6

[Chandra Bhatt]

If n is non-positive then the pattern will be applied as many times as possible and the array can have any length.

What have you concluded by this API quote and your practical
findings when the limit is non positive. The output looks
obscure to me!

And Yeah,
What you call "space" is not space actually, they are blank
Strings,

Excerpts of your code goes below:

String str = "abcdabcdabcdaa";

String[] tokens = str.split("a",-2);
for(String s:tokens){
         System.out.println(">"+s+"<");      [B]//space,bcd,bcd,bcd,space,space[/B]
}
System.out.println(tokens.length);

Please clarify!!!


Thanks,
cmbhatt
[ April 24, 2007: Message edited by: Chandra Bhatt ]

[Meena R. Krishnan]

Yes, by space I meant a blank space. See the o/p posted following that.

The eg. is mainly to see how it works as per the API doc.

When the limit is a non-positive number, the pattern is searched-for repeatedly until the end of the string and it returns the trailing spaces, if any.
In the eg. string "abcdabcdabcdaa", the last two 'a's return empty strings.
o/p:

><
>bcd<
>bcd<
>bcd<
><
>< 

Also, in this case, no matter what the number is -1 or -10 or whatever, the result is the same. Why? I'm not sure.


Zero or no limit split:
In the case of a split with no limit or with zero limit, the last two 'a's were not returned, thereby as per the API, the trailing spaces were not returned.

><
>bcd<
>bcd<
>bcd<

Why it is behaving differently? that's a question for the java experts.