How to use regular expression in scala?

Question

I am learning Scala and spark and want to get the numbers out of string. And for that i am using the regular expression. And came to know about the weird signature of using regular patterns in Scala.

Here is my code:

val myString: String = "there would be some number here 34."
val pattern = """.* ([\d]+).*""".r  
val pattern(numberString) = myString
val num = numberString.toInt
println(answer)

The code is working fine, but seems a bit weird and less readable.

Is there any other way to do this in Scala? Or any other syntax which i can use?

Well, I am going through a similar tutorial and I am unable to grasp my mind around this syntax. It feels pretty weird to see the result part be part of a function call? val pattern(numberString) = myString. Could anyone explain that? — Zaid Khan
– Zaid Khan, Commented Sep 18, 2021 at 11:08

Wiktor Stribiżew · Accepted Answer · 2019-03-07 09:04:53Z

2

The pattern-matching way you are extracting the number is rather resource consuming: since the pattern must match the whole string, you have to add .* on both ends of the regex, and that triggers a lot of backtracking. You also added a space to make sure the first .* does not eat all the digits on the left and return all 1+ digits found.

If you are looking for a first match, use findFirstIn:

val myString: String = "there would be some number here 34."
val numberString = """\d+""".r.findFirstIn(myString)
val num = numberString.get.toInt
println(num) // => 34

See the Scala demo.

answered Mar 7, 2019 at 9:04

Wiktor Stribiżew

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