Java's Asynchronous Ecosystem

Java has accumulated a diverse toolbox for concurrency and asynchrony over the decades, ranging from classic threads to parallel streams, from Future to CompletableFuture, and from reactive libraries to the latest innovations, including virtual threads, structured concurrency, and the Vector API. But with so many options, the question is: which ones should we use today, which still matter, and which belong in the history books?

In this talk, we’ll explore the entire spectrum:

• Classic Threads – the original concurrency primitive.
• Parallel Streams – data parallelism for the collections era.
• Futures & CompletableFuture – async results with callbacks and chaining.
• Reactive Programming – backpressure, publishers, and the rise of frameworks like Reactor and RxJava.
• Virtual Threads – Lightweight Concurrency Made Mainstream.
• Structured Concurrency – Taming async chaos with lifetimes and scopes.
• Vector API – data-level parallelism on modern CPUs.

We’ll also tackle the hard questions:

• Do virtual threads really kill the need for reactive programming?
• What do developers mean by “hidden stack traces,” and how do they impact debugging and profiling?
• Where should you invest today, and what patterns should you abandon permanently?