The Hitchhiker Guide to Pure Functions and Immutable Objects
summary
Defines pure functions as side‑effect free and deterministic, shows Java cannot enforce purity at compile or runtime, and prescribes a concrete pattern: isolate a functional core of pure functions and surround it with an imperative shell that does I/O. Demonstrates Java techniques: use self‑validating constructors, immutable value objects (use records on Java 17 or Lombok pre‑17), refactor with split‑phase to push reads/writes outward, avoid mutating collections (cloning lists hurts GC), and notes memoization of pure functions remains pure.
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chapters (7)
- 0:00Introduction and speaker background
- 1:49Problems with impure code
- 9:12Pure functions explained
- 17:12Why immutable objects matter
- 25:39Value vs reference objects
- 30:52When to use immutability
- 31:33Q&A: Memoization and purity
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