Java Concurrency: A Journey from Threads to Structured Concurrency

This article traces the evolution of Java concurrency, from raw threads in Java 1 to structured concurrency in Java 21. Early Java concurrency involved manual thread management, leading to various issues. Java 5 introduced ExecutorService, simplifying thread lifecycle management; Java 7's ForkJoinPool optimized for CPU-bound tasks; Java 8's CompletableFuture enabled non-blocking task chaining; Java 9's Flow API supported reactive programming; and Java 21's virtual threads and structured concurrency further enhance efficiency and safety, addressing previous challenges and offering a safer, cleaner way to handle concurrent tasks.