Data Structures Overview

Clojure’s core collections are immutable and persistent. Most of the “how do I model this?” questions for Java developers come down to choosing the right collection shape and using the right update functions.

This section gives you a compact view of vectors, lists, maps, and sets, including the operations you’ll see constantly in real code (assoc, update, conj, get, into).

In this section

• Lists
  When to use Clojure’s immutable linked lists (mostly for code and stack-like operations) and how conj/cons/first/rest behave.
• Vectors
  Clojure’s default ordered collection: persistent vectors with fast indexed access, assoc updates, and conj at the end.
• Maps
  Clojure’s go-to “record” type: persistent maps with keyword keys, fast lookup, and immutable assoc/update/merge operations.
• Sets
  Unique collections with fast membership tests: create sets, add/remove items, and use clojure.set for union/intersection/difference.
• Keywords and Symbols
  How keywords and symbols differ: keywords are self-evaluating identifiers (often map keys); symbols resolve to vars/functions.