Type checking on user input Scala Spark - scala

Question

I'm trying to do a type checking on an input that the user insert, but I don't know ho to do.
My code is:
for(iteration<- 0 to 19) {
print(movieRecommended(iteration))
var personalRate = scala.io.StdIn.readDouble()
if(Try(personalRate.toInt).isSuccess){
while((personalRate > 5 || personalRate < 1) || personalRate % 0.5 != 0) {
println("Error: respect the parameters")
print(movieRecommended(iteration))
personalRate = scala.io.StdIn.readDouble()
}
}
else println("Error")
ratingArr(iteration) = personalRate
}
But when I try to give a string input like "a" I receive this error:
Exception in thread "main" java.lang.NumberFormatException: For input string: "a"
at java.base/jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2054)
at java.base/jdk.internal.math.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
at java.base/java.lang.Double.parseDouble(Double.java:549)
at scala.collection.immutable.StringLike.toDouble(StringLike.scala:321)
at scala.collection.immutable.StringLike.toDouble$(StringLike.scala:321)
at scala.collection.immutable.StringOps.toDouble(StringOps.scala:33)
at scala.io.StdIn.readDouble(StdIn.scala:167)
at scala.io.StdIn.readDouble$(StdIn.scala:162)
at scala.io.StdIn$.readDouble(StdIn.scala:241)
at CollaborativeFilteringUserBasedALS$.$anonfun$askUserInput$1(CollaborativeFilteringUserBasedALS.scala:192)
at scala.collection.immutable.Range.foreach$mVc$sp(Range.scala:158)
at CollaborativeFilteringUserBasedALS$.askUserInput(CollaborativeFilteringUserBasedALS.scala:189)
at CollaborativeFilteringUserBasedALS$.topRated(CollaborativeFilteringUserBasedALS.scala:133)
at CollaborativeFilteringUserBasedALS$.main(CollaborativeFilteringUserBasedALS.scala:284)
at CollaborativeFilteringUserBasedALS.main(CollaborativeFilteringUserBasedALS.scala)
Someone can explain me what I'm doing wrong?

Answer 1

You can read the input as a string using scala.io.StdIn.readLine() then try to parse it to Int and use pattern matching to handle case for valid int and for error.
Something like this :
for (iteration <- 0 to 19) {
var personalRate = scala.io.StdIn.readLine()
Try(personalRate.toInt).toOption match {
case Some(rate) => {
println(rate)
// your logic for int
}
case _ => println("Error")
//...
}
}