[Solved] Given a list of nullable Strings, how do you create a list of their lengths, ignoring nulls safely? — Ans: val lengths = list.mapNotNull { it?.length } | Kotlin

Kotlin - Null Safety

Given a list of nullable Strings, how do you create a list of their lengths, ignoring nulls safely?

Aval lengths = list.map { it.length }

Bval lengths = list.mapNotNull { it?.length }

Cval lengths = list.filter { it != null }.map { it.length }

Dval lengths = list.map { it?.length ?: 0 }

Step-by-Step Solution

Solution:

Step 1: Understand list of nullable Strings
Elements can be null, so safe handling is needed.
Step 2: Use mapNotNull with safe call
mapNotNull applies function and removes null results safely.
Final Answer:
val lengths = list.mapNotNull { it?.length } -> Option B
Quick Check:
mapNotNull + safe call = filtered non-null lengths [OK]

Quick Trick: Use mapNotNull with '?.' to skip nulls safely [OK]

Common Mistakes:

MISTAKES

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Given a list of nullable Strings, how do you create a list of their lengths, ignoring nulls safely?