How to "Catch" both a non-numeric and Incomplete ArrayList capacity - kotlin

Question

I created an ArrayList that has a capacity of 5 Ints. I can get the if statement to run if its less than 5 but I can't seem to get the else statement to "Catch" Non-Numerics. For example if I enter 1,2,3,Hello; it will print "Wrong number of sales provided."
fun main(){
val stats = ArrayList<Int>(5)
println("Enter your numbers: ")
try {
while (stats.size < 5) {
stats.add(readLine()!!.toInt())
}
}catch (e: NumberFormatException){
if (stats.size != 5){
println("The wrong number of sales provided.")
}else{
println("All inputs should be numeric.")
}
exitProcess(status = 1)
}
calStats(stats)
}
fun calStats(sales: Collection<Int>){
val min = sales.minOrNull()
val max = sales.maxOrNull()
println("Min: $min\nMax: $max\nRange: ${(max!! - min!!)}\nAverage: ${(BigDecimal(sales.average()).setScale(0, RoundingMode.FLOOR))} ")
}

Answer 1

The problem is how you are handling your exception, in fact since you are checking the size of your array first, if you enter 1,2,3,'Hello' and there are 4 elements in this list it will output the wrong message.
You should nest your try ... catch block inside the while loop.
Actually the if (stats.size != 5) control is reduntant since the while loop will execute until stats has a size of 5, unless the NumberFormatException is thrown.
Try to edit your code like this:
fun main() {
val stats = ArrayList<Int>(5)
println("Enter your numbers: ")
while (stats.size < 5) {
try {
stats.add(readLine()!!.toInt())
} catch (e: NumberFormatException) {
println("All inputs should be numeric.")
exitProcess(status = 1)
}
}
calStats(stats)
}

Answer 2

Your logic loops through, reading lines and adding them until you've collected 5 values. As soon as it fails at parsing one of those lines as an Int, it throws a NumberFormatException and you hit the catch block.
The first thing the catch block does is check how many values you've successfully added to the stats list. If it's not exactly 5, it prints the "wrong number" error instead of the "inputs need to be numeric" one.
But if you think about it, the size is never going to be 5 when you hit the catch block - if you've added 5 items successfully, the while loop ends and there's no way it's going to throw. If you have 4 items and the 5th one fails, it doesn't get added, so you have 4 items when you hit the catch block.
If you need to do it this way, you probably want to keep a counter of how many lines you've read and refer to that. But you'll still throw once you hit the first non-numeric value (even if there's 5 of them to be read in total) and the counter will show how far you've got, not how many there are.
Probably the easiest way is to read in 5 lines to a list, and then transform them to Ints and add those to your collection. That way you can check if you have less than 5 before you start, and handle that case separately.
Something like
// create a list by calling readline() 5 times - produces null at EOF
val lines = List(5) { readLine() }
if (lines.contains(null)) { // handle your "not enough items" here }
// parse all lines as Ints - any that fail will be null
val stats = lines.map { it.toIntOrNull() } // or map(String::toIntOrNull)
if (stats.contains(null)) { // handle bad values here }
Kotlin's style tries to avoid exceptions, which is why you have functions like toIntOrNull alongside toInt - it lets you use nulls as a "failure value" that you can handle in normal code. But you can always throw an exception if you want (e.g. when you get a null line) and handle it in your catch block.