Getting null pointer exception in kotlin

Question

The sum of a = 2.3 and b = 1.9 and the result should be 4.

So what I tried is to round the number by converting to Int but I am getting null pointer exception.

fun main() {

    val a = readLine()!!.trim().toFloat()
    val b = readLine()!!.trim().toFloat()
    val result = addNumbers(a,b)
}
fun addNumbers(a:Float, b:Float):Int{ //I should not change this function
    return a.toInt()+b.toInt()
}

Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — a_local_nobody, Aug 24 '19 at 19:27

score 1 · Answer 1 · answered Aug 09 '19 at 19:47

You are likely running in some context where there's no standard input (such as https://play.kotlinlang.org/, just for an example), because that's when readLine() returns null:

Return the line read or null if the input stream is redirected to a file and the end of file has been reached.

Phash · Answer 2 · 2019-08-10T09:42:10.637

0

please provide the readLine() function. You use it as "throw an NPE if it is null" by adding !! to the call. Better would be

fun main() {

    val a = readLine()?.trim().toFloat()?: 0
    val b = readLine()?.trim().toFloat()?: 0
    val result = addNumbers(a,b)
}
fun addNumbers(a:Float, b:Float):Int{ //I should not change this function
    return a?.toInt()?:0+b?.toInt()?:0
}

there you get a 0 to add, when readLine is null

edited Aug 10 '19 at 09:42

answered Aug 09 '19 at 16:06

Phash

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2
7

But I can't edit that main function. Is there any alternative by applying in addNumbers function? – Star Aug 09 '19 at 16:14
@Phash I assume it's the default https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.io/read-line.html. – Alexey Romanov Aug 09 '19 at 19:50
Updated the andere. Look at the addNumbers function – Phash Aug 10 '19 at 09:42

Getting null pointer exception in kotlin

2 Answers2