Asynchronous Programming with CompletableFuture.

CompletableFuture is an extension to Java's Future API that supports functional-style callbacks and complex task chaining.

Key Capabilities:

• Chaining: thenApply(), thenAccept(), thenRun().
• Composition: thenCompose() (like flatMap), thenCombine() (combining two futures).
• Error Handling: exceptionally(), handle().
• Async Execution: By default, uses the ForkJoinPool.commonPool() unless a custom executor is provided.