Kotlin - Collections Fundamentals
Which Kotlin expression safely accesses the value for key "x" in a map and returns 0 if the key is missing?
Which Kotlin expression safely accesses the value for key "x" in a map and returns 0 if the key is missing?
easy📝 Conceptual Q2 of 15
Step-by-Step Solution
Solution:
Step 1: Understand map access and default values
Usingmap["x"]returns the value or null if key is missing. The Elvis operator?:provides a default value if null.Step 2: Check each option
map["x"] ?: 0 uses?: 0to return 0 if key "x" is missing. map.get("x") returns nullable value without default. map["x"]!! forces non-null and throws if missing. map.getValue("x") throws if key missing.Final Answer:
map["x"] ?: 0 -> Option CQuick Check:
Safe map access with default = map["x"] ?: 0 [OK]
Quick Trick: Use ?: to provide default when accessing nullable map values [OK]
Common Mistakes:
MISTAKES- Using !! which throws exception if key missing
- Using getValue which throws if key missing
- Not providing default value for null
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