Sets and Lists in Java: When to Use Which?

Understanding the Distinction between Sets and Lists

When working with data collections in Java, it's crucial to distinguish between sets and lists. Both interfaces, Set and List, provide different functionalities and behaviors.

Sets vs Lists: Key Differences

The fundamental difference between Set and List lies in their ordering and uniqueness of elements.

• Sets:

  • Represent unordered collections without duplicate elements.
  • Elements are automatically sorted by the implementation's hash code.

• Lists:

  • Represent ordered sequences of elements.
  • Elements maintain their insertion order and can have duplicates.

Implementation Details

Set

Set is implemented by HashSet, TreeSet, and LinkedHashSet.

• HashSet: An unordered, unsorted collection with quick lookups and insertions but no predictable ordering.
• TreeSet: An ordered collection that maintains a natural (ascending) ordering of elements.
• LinkedHashSet: An ordered collection that combines the features of a HashSet and a linked list, providing predictable iteration order.

List

List is implemented by ArrayList, LinkedList, and Vector.

• ArrayList: An ordered, resizable array that provides fast random access and element retrieval.
• LinkedList: A doubly-linked list that allows for efficient insertions and removals at any position. It supports null elements.
• Vector: A synchronized version of ArrayList that ensures thread safety.

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