Scala | String Interpolation

String Interpolation refers to substitution of defined variables or expressions in a given String with respected values. String Interpolation provides an easy way to process String literals. To apply this feature of Scala, we must follow few rules:

1. String must be defined with starting character as s / f /raw.
2. Variables in the String must have '$' as prefix.
3. Expressions must be enclosed within curly braces ({, }) and '$' is added as prefix.

Syntax:

 // x and y are defined val str = s"Sum of $x and $y is ${x+y}"

Types of String Interpolator

1. s Interpolator: Within the String, we can access variables, object fields, functions calls, etc. Example 1: variables and expressions: scala

   // Scala program // for s interpolator // Creating object object GFG {   // Main method  def main(args:Array[String])  {    val x = 20  val y = 10    // without s interpolator  val str1 = "Sum of $x and $y is ${x+y}"  // with s interpolator  val str2 = s"Sum of $x and $y is ${x+y}"    println("str1: "+str1)  println("str2: "+str2)  } } 

   Output:

   str1: Sum of $x and $y is ${x+y} str2: Sum of 20 and 10 is 30

   Example 2: function call scala

   // Scala program // for s interpolator // Creating object object GFG {   // adding two numbers  def add(a:Int, b:Int):Int  =  {   a+b   }    // Main method  def main(args:Array[String])  {    val x = 20  val y = 10    // without s interpolator  val str1 = "Sum of $x and $y is ${add(x, y)}"  // with s interpolator  val str2 = s"Sum of $x and $y is ${add(x, y)}"    println("str1: " + str1)  println("str2: " + str2)  } } 

   Output:

   str1: Sum of $x and $y is ${add(x, y)} str2: Sum of 20 and 10 is 30

2. f Interpolator: This interpolation helps in formatting numbers easily. To understand how format specifiers work refer Format Specifiers. Example 1: printing upto 2 decimal place: scala

   // Scala program // for f interpolator // Creating object object GFG {   // Main method  def main(args:Array[String])  {    val x = 20.6    // without f interpolator  val str1 = "Value of x is $x%.2f"  // with f interpolator  val str2 = f"Value of x is $x%.2f"    println("str1: " + str1)  println("str2: " + str2)    } } 

   Output:

   str1: Value of x is $x%.2f str2: Value of x is 20.60

   Example 2: setting width in integers: scala

   // Scala program // for f interpolator // Creating object object GFG {   // Main method  def main(args:Array[String])  {    val x = 11    // without f interpolator  val str1 = "Value of x is $x%04d"  // with f interpolator  val str2 = f"Value of x is $x%04d"    println(str1)  println(str2)  } } 

   Output:

   Value of x is $x%04d Value of x is 0011

   If we try to pass a Double value while formatting is done using %d specifier, compiler outputs an error. In case of %f specifier, passing Int is acceptable.
3. raw Interpolator: String Literal should start with ‘raw’. This interpolator treats escape sequences same as any other character in a String. Example :printing escape sequence: scala

   // Scala program // for raw interpolator // Creating object object GFG {   // Main method  def main(args:Array[String])  {    // without raw interpolator  val str1 = "Hello\nWorld"  // with raw interpolator  val str2 = raw"Hello\nWorld"    println("str1: " + str1)  println("str2: " + str2)  } } 

   Output:

   str1: Hello World str2: Hello\nWorld