String split

[Chetan Parekh]

1|2|3||5||

How to split above String value in to an array with 7 elements. 3rd, 5th and 6th will have null as a value.

String elements[] = s.split("[|]");

Above code generate array with 5 elements only. Last two elements with null value are not getting generated.

[Chetan Parekh]

Got it!

String element[] = s.split("[|]", -1);

[Campbell Ritchie]

Do you get two nulls or two empty Strings? An empty string and a null are completely different from each other.

[Chetan Parekh]

Thanks !

I got the empty String. I just have to verify the resultant array's length, so I am fine with either.

[John Laker]

Chetan Parekh wrote:Got it!

String element[] = s.split("[|]", -1);

Can you explain that code a little bit ? What does the -1 do ?

[Darryl Burke]

John Laker wrote:

Can you explain that code a little bit ? What does the -1 do ?

It's all there n the API for String#split(...)
The limit parameter controls the number ... If n is non-positive then ...

[John Laker]

Darryl Burke wrote:

John Laker wrote:

Can you explain that code a little bit ? What does the -1 do ?

It's all there n the API for String#split(...)
The limit parameter controls the number ... If n is non-positive then ...

Yes I read it, but had difficulty undestanding this quote there

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.

I'm not sure what pattern they are talking about and how it is applied to what.

[T. Huy Nguyen]

John Laker wrote:

Yes I read it, but had difficulty undestanding this quote there

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.

I'm not sure what pattern they are talking about and how it is applied to what.

The 1st argument to split() is a regex pattern.

And if the 2nd parameter is negative (-1), nothing is discarded. So the result is an array with 7 elements with the last 2 are empty stringS. These last 2 elements will be discarded if split("[|]") or split ("[|]", 0) are used

[John Laker]

T. Huy Nguyen wrote:

The 1st argument to split() is a regex pattern.

And if the 2nd parameter is negative (-1), nothing is discarded. So the result is an array with 7 elements with the last 2 are empty stringS. These last 2 elements will be discarded if split("[|]") or split ("[|]", 0) are used

I see. The second part makes sense now.

Another question, What is a regex pattern ? I understand that in this example it is "|" which is used to split the string, but what is like a simple definition. Google search did not yield satisfactory results.

[T. Huy Nguyen]

If you don't know much about regular expression, Wikipedia is a good start. More complete cover of regex and regex support in major programming languages can be found in the book "Mastering regular expression".

But I think a bit of wiki and the javadoc of Pattern class (http://download.oracle.com/javase/6/docs/api/java/util/regex/Pattern.html) are good enough.

[Stephan van Hulst]

A regex or 'regular expression' is a description of what a String looks like. For example, the pattern "[\\p{Print}&&[^\\\\/:*?\"<>|]]{0,8}" is a description for a string that is between 0 and 8 characters long, and consists of any printable character, except the characters \ / : * ? " < > |

As you can see, regular expressions can become illegible very quickly. To fully understand them you should probably look up a tutorial on regular expressions.