26 — Concurrency

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▶️ pkg7concurrency/concurrency1ThreadBasics.java → concurrency8LocksAndCoordination.java
▶️ Advanced: pkg16advconcurrency/

Core concepts

Building blocks

1// Thread2Thread t = Thread.startVirtualThread(() -> task());  // Java 213 4// ExecutorService5ExecutorService pool = Executors.newFixedThreadPool(4);6Future<Integer> f = pool.submit(() -> compute());7 8// CompletableFuture9CompletableFuture.supplyAsync(() -> fetch())10    .thenApply(data -> transform(data))11    .thenAccept(System.out::println);12 13// Synchronization14synchronized (lock) { ... }15ReentrantLock lock = new ReentrantLock();16AtomicInteger counter = new AtomicInteger();

Virtual threads (Java 21)

Millions of cheap threads for blocking I/O. Don't pool them like platform threads.

⚠️ Pinning: synchronized inside virtual thread may pin to carrier thread.

Learning order

1. concurrency1 Thread basics
2. concurrency2 Runnable / Callable
3. concurrency3 ExecutorService
4. concurrency4 synchronized / volatile
5. concurrency5 Concurrent collections
6. concurrency6 CompletableFuture
7. concurrency7 Virtual threads
8. concurrency8 Locks

Deep dive → 04 Concurrency

Next → 27 Design Patterns