What is the difference between `HashMap`’s `get()` time complexity and worst-case time complexity, and what causes worst-case?

Question

Java Associate — Hard

What is the difference between `HashMap`’s `get()` time complexity and worst-case time complexity, and what causes worst-case?

Accepted Answer

The difference between `HashMap`'s `get()` time complexity and worst-case time complexity is due to hash collisions. In the worst-case scenario, all keys map to the same bucket, leading to O(n) complexity. However, in the average case, it is O(1) due to constant time access.