completablefuture join vs get

Question

下面是我的代码：

List<String> process() {

    List<String> messages = Arrays.asList("Msg1", "Msg2", "Msg3", "Msg4", "Msg5", "Msg6", "Msg7", "Msg8", "Msg9",
            "Msg10", "Msg11", "Msg12");
    MessageService messageService = new MessageService();
    ExecutorService executor = Executors.newFixedThreadPool(4);

    List<String> mapResult = new ArrayList<>();

    CompletableFuture<?>[] fanoutRequestList = new CompletableFuture[messages.size()];
    int count = 0;
    for (String msg : messages) {
        CompletableFuture<?> future = CompletableFuture
                .supplyAsync(() -> messageService.sendNotification(msg), executor).exceptionally(ex -> "Error")
                .thenAccept(mapResult::add);

        fanoutRequestList[count++] = future;
    }

    try {
        CompletableFuture.allOf(fanoutRequestList).get();
      //CompletableFuture.allOf(fanoutRequestList).join();
    } catch (InterruptedException | ExecutionException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    return mapResult.stream().filter(s -> !s.equalsIgnoreCase("Error")).collect(Collectors.toList());
}

这两种方法我都试过了，但我看不出结果有什么不同。

Answer 1

唯一的区别是方法如何抛出异常。get()在future接口中声明为

V get() throws InterruptedException, ExecutionException;

这两个异常都是检查异常，这意味着它们需要在代码中处理。正如您在代码中看到的那样，IDE中的自动代码生成器询问是否为您创建try-catch块。

try {
  CompletableFuture.allOf(fanoutRequestList).get() 
} catch (InterruptedException | ExecutionException e) {
  // TODO Auto-generated catch block
  e.printStackTrace();
}

join()方法不引发检查异常。

public T join()

CompletableFuture<List<String>> cf = CompletableFuture
    .supplyAsync(this::process)
    .exceptionally(this::getFallbackListOfStrings) // Here you can catch e.g. {@code join}'s CompletionException
    .thenAccept(this::processFurther);