What is the meaning of Error..Whats wrong in my code..Kotlin

Question

Code
fun main(args: Array<String>){
var a: Int= readLine ()!! .toInt()
var fact=1
while(a<=1){
a--
if(a>=1){
fact=fact*a
}
else{
println("Enter correct no.")
}
}
println(fact)
}

Error:
Exception in thread "main" java.lang.NullPointerException
at FileKt.main (File.kt:2)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (:-2)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (:-1)

Answer 1

Your code is very difficult to read.
It is always better to save it on the code playground, and insert a link in your question.
I reformatted and fixed your code, please check.

https://code.sololearn.com/c7ve0zGr17pN/?ref=app

- there must be no whitespace between readline and the parentheses, because it is a function invocation
- changed the relational operator in your while loop condition, otherwise the loop wouldn't run even once.
- the if condition inside the loop is redundant. If you want to validate the input, better to do it before starting the loop.
- the variable a should be decremented only after the multiplication

Proper formatting, indentation, and whitespaces around operators, gives much easier readability. Write tidy and clean code! :)