[Solved] What does the Kotlin expression map[key] ?: "default" do? — Ans: Returns the value for key if it exists, otherwise returns "default". | Kotlin

Kotlin - Collections Fundamentals

What does the Kotlin expression map[key] ?: "default" do?

ARemoves the <code>key</code> from the map if it exists.

BReturns the value for <code>key</code> if it exists, otherwise returns "default".

CThrows an error if <code>key</code> is not in the map.

DAlways returns "default" regardless of <code>key</code>.

Step-by-Step Solution

Solution:

Step 1: Understand map access with []
Accessing map[key] returns the value if key exists, or null if it doesn't.
Step 2: Use the Elvis operator ?: for fallback
The expression ?: "default" means if the left side is null, return "default" instead.
Final Answer:
Returns the value for key if it exists, otherwise returns "default". -> Option B
Quick Check:
map[key] ?: default = safe access with fallback [OK]

Quick Trick: Use ?: to provide a default when key might be missing [OK]

Common Mistakes:

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What does the Kotlin expression map[key] ?: "default" do?