Kotlin - Null Safety
Consider this Kotlin code:
val list: MutableList = mutableListOf("a", "b", "c")
list.add(null)
println(list.size)
What happens when you run it?
Consider this Kotlin code: val list: MutableList = mutableListOf("a", "b", "c") list.add(null) println(list.size) What happens when you run it?
medium📝 Predict Output Q5 of 15
Step-by-Step Solution
Solution:
Step 1: Check list type and add operation
The list is MutableList, which does not allow null elements. Trying to add null is not allowed by the compiler. Step 2: Understand Kotlin's compile-time null safety
Kotlin prevents adding null to non-nullable collections at compile time, so this code will not compile.Final Answer:
Compilation error due to adding null to non-nullable list -> Option AQuick Check:
Adding null to non-nullable list = compile error [OK]
Quick Trick: Cannot add null to non-nullable collection types [OK]
Common Mistakes:
MISTAKES- Expecting runtime exception instead of compile error
- Assuming null is added silently
- Thinking size prints 4 despite error
Master "Null Safety" in Kotlin
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