The guided path through Java. Read top-to-bottom for a cold refresh, or jump to
a section. Links in italics aren’t written yet — they’re your to-do list.
1. Language core
Start here — these show up in almost every Java interview.
- Java Generics — Bounded, Unbounded & PECS
- OOPS — four pillars, and how you’d defend a design choice
- Records — immutable data carriers (Java 16+)
- Optional — the right and wrong ways to use it
- Lambda — functional interfaces, method references
2. Collections
- Collections — List/Set/Map families, when to use which
- HashMap — internals, resizing, treeification
- Entry — the node structure behind the map
3. JVM & runtime
- GC — generational collection, common collectors, tuning basics
4. Concurrency (high-value, build these next)
- CompletableFuture — async composition,
thenComposevsthenCombine - ExecutorService — thread pools, sizing, shutdown
Test-yourself sweep
Before an interview, open each note above and answer its Test Yourself block
from memory before revealing. If you miss one, that’s tomorrow’s revision.
Refresher tag
Any note you tag
#refresheralso shows up in your auto-built
Refresher index — use it for the ones you forget most.