Given a mutable map val map = mutableMapOf("x" to 5), which code adds a new key "y" with value 10 only if "y" is not already present?

hard📝 Application Q9 of 15

Kotlin - Collections Fundamentals

Given a mutable map val map = mutableMapOf("x" to 5), which code adds a new key "y" with value 10 only if "y" is not already present?

Amap.putIfAbsent("y", 10)

Bmap.put("y", 10)

Cmap["y"] = 10

Dmap.add("y", 10)

Step-by-Step Solution

Solution:

Step 1: Understand putIfAbsent behavior
putIfAbsent adds the key-value only if key is missing.
Step 2: Check other methods
map["y"] = 10 and put() overwrite existing keys; add() is invalid for maps.
Final Answer:
map.putIfAbsent("y", 10) -> Option A
Quick Check:
Use putIfAbsent to add only if key missing = C [OK]

Quick Trick: Use putIfAbsent to avoid overwriting existing keys [OK]

Common Mistakes:

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