Kotlin - Null Safety
Find the issue in this Kotlin code:
val list: MutableList = mutableListOf("a", "b")
list.add(null)
list.forEach { println(it.length) }
Find the issue in this Kotlin code: val list: MutableList = mutableListOf("a", "b") list.add(null) list.forEach { println(it.length) }
medium📝 Debug Q7 of 15
Step-by-Step Solution
Solution:
Step 1: Understand list type and null addition
The list allows nulls because element type is String?. Adding null is valid.Step 2: Analyze forEach usage
Inside forEach, it.length is called without safe call operator. Since it can be null, this causes a runtime NullPointerException.Final Answer:
Calling length on a nullable String without safe call causes a runtime exception. -> Option AQuick Check:
Nullable elements require safe calls to avoid exceptions [OK]
Quick Trick: Use ?.length for nullable strings to avoid exceptions [OK]
Common Mistakes:
MISTAKES- Assuming adding null is invalid
- Thinking forEach cannot iterate MutableList
- Ignoring null safety when accessing properties
Master "Null Safety" in Kotlin
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