Scala Regular Expressions

Scala supports regular expressions through the Regex class in the scala.util.matching package. The following example demonstrates using a regular expression to find the word Scala:

Example

import scala.util.matching.Regex

object Test {
   def main(args: Array[String]) {
      val pattern = "Scala".r
      val str = "Scala is Scalable and cool"
      
      println(pattern findFirstIn str)
   }
}

Running the above code, the output is:

$ scalac Test.scala 
$ scala Test
Some(Scala)

In the example, the r() method of the String class is used to construct a Regex object.

Then the findFirstIn method is used to find the first match.

If you need to see all matches, you can use the findAllIn method.

You can use the mkString( ) method to connect the strings of regular expression matches, and you can use the pipe (|) to set different patterns:

Example

import scala.util.matching.Regex

object Test {
   def main(args: Array[String]) {
      val pattern = new Regex("(S|s)cala")  // The first letter can be uppercase S or lowercase s
      val str = "Scala is scalable and cool"
      
      println((pattern findAllIn str).mkString(","))   // Use a comma , to connect the returned results
   }
}

Running the above code, the output is:

$ scalac Test.scala 
$ scala Test
Scala,scala

If you need to replace the matched text with a specific keyword, you can use the replaceFirstIn( ) method to replace the first match, and use the replaceAllIn( ) method to replace all matches, as shown in the following example:

Example

object Test {
   def main(args: Array[String]) {
      val pattern = "(S|s)cala".r
      val str = "Scala is scalable and cool"
      
      println(pattern replaceFirstIn(str, "Java"))
   }
}

Running the above code, the output is:

$ scalac Test.scala 
$ scala Test
Java is scalable and cool

Regular Expressions

Scala's regular expressions inherit the syntax rules of Java, which mostly uses the rules of the Perl language.

The following table provides some common regular expression rules: