The Future and CompletableFuture classes in Java both represent asynchronous computations, but they have some differences in terms of functionality and usage.
Future:
Syntax:
Future<ResultType> future = executorService.submit(Callable<ResultType> task);
Example:
ExecutorService executor = Executors.newFixedThreadPool(1);
Future<String> future = executor.submit(() -> {
Thread.sleep(2000); // Simulate a time-consuming task
return “Hello, from Future!”;
});
String result = future.get(); // Blocking call to get the result
System.out.println(result);
executor.shutdown();
Future<String> future = executor.submit(() -> {
Thread.sleep(2000); // Simulate a time-consuming task
return “Hello, from Future!”;
});
String result = future.get(); // Blocking call to get the result
System.out.println(result);
executor.shutdown();
CompletableFuture:
Syntax:
CompletableFuture<ResultType> future = CompletableFuture.supplyAsync(Supplier<ResultType> supplier);
Example:
CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> {
try {
Thread.sleep(2000); // Simulate a time-consuming task
} catch (InterruptedException e) {
e.printStackTrace();
}
return “Hello, from CompletableFuture!”;
});
future.thenAccept(result -> System.out.println(result)); // Non-blocking callback
try {
Thread.sleep(2000); // Simulate a time-consuming task
} catch (InterruptedException e) {
e.printStackTrace();
}
return “Hello, from CompletableFuture!”;
});
future.thenAccept(result -> System.out.println(result)); // Non-blocking callback
Differences:
Completion Handling:
Future relies on blocking methods like get() for result retrieval, while CompletableFuture provides non-blocking methods like thenAccept() for completion handling.
Composition:
CompletableFuture supports fluent API and allows chaining of multiple asynchronous operations, whereas Future does not.
Explicit Completion:
CompletableFuture allows explicit completion via methods like complete() or completeExceptionally(), which can be useful in certain scenarios.
