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Concurrency Intermediate

Wait and notify queues to BlockingQueue

Replace hand-written producer-consumer coordination with BlockingQueue.

Concurrency
Code Comparison
✕ Manual wait and notify 
synchronized (queue) {
    while (queue.isEmpty()) {
        queue.wait();
    }
    Job job = queue.removeFirst();
    process(job);
}
✓ BlockingQueue 
BlockingQueue<Job> queue = new LinkedBlockingQueue<>();

Job job = queue.take();
process(job);
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Why the modern way wins
🛡

Safer coordination

The queue owns the locking and condition signaling.

👁

Clear intent

put() and take() directly express producer-consumer behavior.

🎛

Built-in policies

Choose bounded capacity, fairness, timeouts, or non-blocking operations.

Old Approach
Manual wait and notify
Modern Approach
BlockingQueue
Since JDK
5
Difficulty
Intermediate
JDK Support
Wait and notify queues to BlockingQueue
Available

Widely available since JDK 5 (2004)

How it works

Correct wait/notify code requires a shared monitor, condition loops, matching notifications, and careful interruption handling. BlockingQueue encapsulates those rules and provides blocking, timed, and non-blocking operations for producer-consumer workflows. Calls such as put() and take() remain interruptible.

Related Documentation
BlockingQueue ↗ LinkedBlockingQueue ↗
Proof
View proof source ↗
Related patterns
Concurrency Beginner

ExecutorService auto-close

Java 8
ExecutorService exec =
    Executors.newCachedThreadPool();
try {
    exec.submit(task);
} finally {
    exec.shutdown();
    exec.awaitTermination(
        1, TimeUnit.MINUTES);
}
Java 19+
try (var exec =
        Executors.newCachedThreadPool()) {
    exec.submit(task);
}
// auto shutdown + await on close
Hover to see modern ➜
JDK 19+ →
Concurrency Advanced

Structured concurrency

Java 8
ExecutorService exec =
    Executors.newFixedThreadPool(2);
Future<User> u = exec.submit(this::fetchUser);
Future<Order> o = exec.submit(this::fetchOrder);
try {
    return combine(u.get(), o.get());
} finally { exec.shutdown(); }
Java 25 (Preview)
try (var scope = new StructuredTaskScope
        .ShutdownOnFailure()) {
    var u = scope.fork(this::fetchUser);
    var o = scope.fork(this::fetchOrder);
    scope.join().throwIfFailed();
    return combine(u.get(), o.get());
}
Hover to see modern ➜
JDK 25+ →
Concurrency Beginner

Virtual threads

Java 8
Thread thread = new Thread(() -> {
    System.out.println("hello");
});
thread.start();
thread.join();
Java 21+
Thread.startVirtualThread(() -> {
    IO.println("hello");
}).join();
Hover to see modern ➜
JDK 21+ →