[Solved] Given a list of Any objects, how can you safely cast all elements to String and collect only the successful casts?val items: List = listOf("a", 1, "b", 2) // Fill in the blank val strings = items.... | Kotlin

Kotlin - Null Safety

Given a list of Any objects, how can you safely cast all elements to String and collect only the successful casts?

val items: List = listOf("a", 1, "b", 2)
// Fill in the blank
val strings = items.mapNotNull { it ___ }

Aas? Int

Bas String

Cas? String

DtoString()

Step-by-Step Solution

Solution:

Step 1: Understand safe cast in mapNotNull
Using as? returns nullable String or null if cast fails.
Step 2: Use mapNotNull to filter nulls
mapNotNull collects only non-null results, so only successful casts remain.
Final Answer:
as? String -> Option C
Quick Check:
Safe cast with mapNotNull filters successful casts = D [OK]

Quick Trick: Use 'as?' inside mapNotNull to filter successful casts [OK]

Common Mistakes:

MISTAKES

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Given a list of Any objects, how can you safely cast all elements to String and collect only the successful casts?