Scala subString function

Question

Hi I am looking for a solution it will return a substring from string for the given indexes.For avoiding index bound exception currently using if and else check.Is there a better approach(functional).

def subStringEn(input:String,start:Int,end:Int)={
  // multiple if check for avoiding index out of bound exception
    input.substring(start,end)
}

Solution 1

Not sure what you want the function to do in case of index out of bound, but slice might fit your needs:

input.slice(start, end)

Some examples:

scala> "hello".slice(1, 2)
res6: String = e

scala> "hello".slice(1, 30)
res7: String = ello

scala> "hello".slice(7, 8)
res8: String = ""

scala> "hello".slice(0, 5)
res9: String = hello

Solution 2

Try is one way of doing it. The other way is applying substring only if length is greater than end using Option[String].

invalid end index

scala> val start = 1
start: Int = 1

scala> val end = 1000
end: Int = 1000

scala> Option("urayagppd").filter(_.length > end).map(_.substring(start, end))
res9: Option[String] = None

valid end index

scala> val end = 6
end: Int = 6

scala> Option("urayagppd").filter(_.length > end).map(_.substring(start, end))
res10: Option[String] = Some(rayag)

Also, you can combine filter and map to .collect as below,

scala> Option("urayagppd").collect { case x if x.length > end => x.substring(start, end) }
res14: Option[String] = Some(rayag)

scala> val end = 1000
end: Int = 1000

scala> Option("urayagppd").collect { case x if x.length > end => x.substring(start, end) }
res15: Option[String] = None