# java-core-examples

Runnable companion code for ankurm.com's Java-core / concurrency series. One Maven module per
article; each module's own README has that article's version table, quickstart, and traps.

| Module | Post |
|---|---|
| [`jmm`](jmm/) | The Java Memory Model Explained: volatile, happens-before, and Why Your Double-Checked Lock Failed |
| [`locks`](locks/) | synchronized vs ReentrantLock vs StampedLock: Benchmarks and a Decision Table |
| [`atomics`](atomics/) | Java Atomics and VarHandle: CAS, LongAdder, and When Atomics Beat Locks |
| [`vt-pinning`](vt-pinning/) | Diagnosing Virtual Thread Pinning in Production: JFR Events, jcmd, and Real Fixes |
| [`synchronizers`](synchronizers/) | CountDownLatch vs CyclicBarrier vs Phaser vs Semaphore in Java |
| [`executors`](executors/) | ExecutorService Done Right: Shutdown, try-with-resources and Virtual Thread Executors |
| [`concurrency-interview`](concurrency-interview/) | Top 40 Java Concurrency Interview Questions and Answers (2026) |
| [`arithmetic`](arithmetic/) | Add Two Numbers in Java Without Overflow: addExact, Widening, and BigInteger |
| [`hashmap-concurrenthashmap`](hashmap-concurrenthashmap/) | Java HashMap vs ConcurrentHashMap: Complete Interview Guide |
| [`exceptions`](exceptions/) | Java Exception Handling Deep Dive: Checked vs Unchecked, Suppression, and What Exceptions Actually Cost |
| [`regex`](regex/) | Java Regex Tutorial: Pattern, Matcher, Groups, Lookarounds and ReDoS |
| [`serialization`](serialization/) | Java Serialization in 2026: Why It's Dangerous and What Replaced It |
| [`strings`](strings/) | Java Strings Deep Dive: Interning, StringBuilder, Text Blocks, and the Concatenation Benchmark |
| [`collections`](collections/) | How to Sort a HashMap by Value (and Key) in Java |
| [`nio2`](nio2/) | Java NIO.2 File API: Files, Path, WatchService, and Streaming Large Files Without OOM |

## License

MIT - see [LICENSE](LICENSE).