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I'm trying to split a text bunch with | bar separator. 123.123.123.123|000.000.000.000 to each ip address blocks. But each numbers are splited not by |.

scala> "123.123.123.123|000.000.000.000".split("|")
res30: Array[java.lang.String] = Array("", 1, 2, 3, ., 1, 2, 3, ., 1, 2, 3, ., 1, 2, 3, |, 0, 0, 0, ., 0, 0, 0, ., 0, 0, 0, ., 0, 0, 0)

scala> "123.123.123.123".split("|")
res33: Array[java.lang.String] = Array("", 1, 2, 3, ., 1, 2, 3, ., 1, 2, 3, ., 1, 2, 3)

So I put the separator as Char and it shows what I intended.

scala> "123.123.123.123|000.000.000.000".split('|')
res31: Array[String] = Array(123.123.123.123, 000.000.000.000)

scala> "123.123.123.123".split('|')
res32: Array[String] = Array(123.123.123.123)

Why does single character make a huge difference?

I've read Scala doc and StringLike.scala, and got no answer.

def split(separators: Array[Char]): Array[String]
def split(separator: Char): Array[String]

Thanks.

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3
  • According to the documentation, split takes a Char as an argument. Commented May 27, 2013 at 7:20
  • 2
    @squiguy not only Char: it can back to java's split, which takes String [regex] Commented May 27, 2013 at 7:20
  • @om-nom-nom Sure, in that case | is special which is obviously what you said in your answer. Commented May 27, 2013 at 7:23

2 Answers 2

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Split method accepts either string or character(s). If you use string it will be interpreted as a regexp and "|" is treated as regex 'or' -- in your case it backs to 'every character goes to it's own bin'. Escape it to have raw delimeter:

"123.123.123.123|000.000.000.000".split("\\|")
res1: Array[String] = Array(123.123.123.123, 000.000.000.000)

Character separator is interpreted as is, so you got the desired result without any fuss

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1 Comment

Thanks @om-nom-nom ! I forgot to remember many of Scala methods are actually from java.lang and java classes. I'll be with javadoc at next time.
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Note that, as om-nom-nom correctly mentioned (but didn't provide the example), characters (which are enclosed in single ') are also valid:

"123.123.123.123|000.000.000.000".split('|')

I find this to be more obvious/readable. I'm also assuming that this would be faster, since it does not have to invoke the regex parser. But that is speculation of course, and also unnecessary micro-optimization.

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5 Comments

It should be considerably faster than regexing - no doubt about that. Actually regexing, in that scenario would simply be a mistake. But the question is not about that, and what you suggest is actually already discovered in the question.
Yes, I said that om-nom-nom had already mentioned it. I just wanted to provide an actual example, since I know many people (including myself) will often only skim an answer for a piece of code, which often is the solution. Since I consider the code example om-nom-nom posted not optimal, I posted my own :)
@x3ro well, I didn't written this because op did it in his examples (res31) ;-) But I do agree that this is likely to be faster than string version
@om-nom-nom: Oh, now I feel a little stupid :D I could swear that it wasn't there when I first read the question, but I've probably just overlooked it... My bad
@x3ro: In other language, I also used to use single quote for all fixed string as the performance concerns you've mentioned above but Scala doesn't seem to be kind for 'string'. What I typed one character with single quotes was a (big) mistake. Thanks to remind me :)

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