CompletableFuture 獲取所有task的結果

前置知識
1，CompletableFuture 使用supplyAsync 可以直接執行，並得到返回結果
2，CompletableFuture get方法，可以得到最終的結果
代碼

private void foreachGet() throws ExecutionException, InterruptedException {
        Random random = new Random();
        long mainstart = System.currentTimeMillis();
        List<CompletableFuture<String>> futureList = new ArrayList<>();
        for (int i = 0; i < 5; i++) {
            CompletableFuture<String> future = CompletableFuture.supplyAsync(()->{
                System.out.println(Thread.currentThread()+",begin");
                long start = System.currentTimeMillis();
                int time = random.nextInt(3000);
                try {
                    Thread.sleep(time);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                long end = System.currentTimeMillis();
                System.out.println(Thread.currentThread()+",cost:"+(end - start));
                System.out.println(Thread.currentThread()+",end");
                return time+"";
            });
            futureList.add(future);
        }

        for (CompletableFuture<String> future : futureList) {
            future.get();
        }
        long mainend = System.currentTimeMillis();
        System.out.println(Thread.currentThread()+" is end:"+(mainend - mainstart));
    }