Data Structures Study Guide 2026

Swift introduced Optionals to safely handle the absence of a value, preventing null pointer exceptions. Java 7 did not have a direct equivalent to Swift's Optional type; `null` was used, which is prone to NullPointerExceptions. Java 8 later introduced `java.util.Optional` to address this, but the question specifically refers to Java 7.

Arrays are typically designed to store a collection of homogeneous data items, meaning all elements must be of the same data type (e.g., an array of integers, an array of strings). Records (structs or objects) and pointers, however, can be used to manage or link non-homogeneous data items.

Binary search halves the search space at each step, requiring at most log₂ n comparisons to find or rule out a target.

Merge sort guarantees O(n log n) in all cases — best, average, and worst — because it always splits evenly and merges linearly.

Merge sort requires O(n) auxiliary space for the temporary arrays used during the merge step.

A queue is a linear data structure that strictly adheres to the First-In, First-Out (FIFO) principle. This means that the first element added to the queue is always the first one to be removed, much like a waiting line in real life. New elements are added to the rear (enqueue), and existing elements are removed from the front (dequeue).