Concurrency vs. Parallelism

Concurrency vs. Parallelism

In this lesson — part of Concurrency Basics — you'll learn concurrency vs. parallelism in Java and why it matters in real work.

Why it matters

Modern programs wait on networks and disks — async lets them stay responsive.

Key ideas

• Blocking vs. non-blocking
• Callbacks, promises, async/await
• Concurrency vs. parallelism
• Error handling in async code

In practice

Here's how it looks in idiomatic Java:

import java.util.concurrent.CompletableFuture;

CompletableFuture.supplyAsync(() -> {
    return 21 * 2;                  // runs on a background thread
}).thenAccept(result -> {
    System.out.println("Got: " + result);
}).join();                          // wait for completion (demo only)

Java note: CompletableFuture is Java's idiomatic async/await equivalent: supplyAsync runs work off-thread and thenAccept/thenApply chain non-blocking callbacks on the result.

Try it yourself

Exercise: In Java, fetch two things concurrently and combine the results.

Recap

You now understand concurrency vs. parallelism and can apply it in Java. Mark this lesson complete and continue to the next one.