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String split function and "||" String

Khaled Mahmoud
Ranch Hand

Joined: Jul 15, 2006
Posts: 361
Hi all,
I have a String like the following : "A || B || C || D || E || F || G || H";

The expected outcome for this code is : 8
The real outcode is : 37

Is this a bug in the split function in the String object.

Please help

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Joanne Neal

Joined: Aug 05, 2005
Posts: 3742
Originally posted by Khaled Mahmoud:
Is this a bug in the split function in the String object.

No. The parameter you pass to the split method is a regular expression and | is a special character in regular expressions. If you don't want it to be regarded as a special character you need to escape it. Note however that the escape character (\) is a special character in Java Strings, so you need to escape that as well. Try

Rob Spoor

Joined: Oct 27, 2005
Posts: 20279

As Joanne said, | is a special character in regular expressions. It means choice. Therefore, || means "empty string or empty string or empty string", in other words: empty string.

Now you may think: that would lead to 36 empty strings, because there are only 36 characters: one empty string before each character. The magic here is, there is also an empty string at the end that matches. Hence 37.

You might want to extend your expression to "\\s*\\|\\|\\s*" to include the spaces (whitespace) as well. \s (unescaped) means all whitespace characters, so that includes spaces. The * means zero or more times, so this regex means: || with any number of whitespace characters before or after it.

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