Java 1.8 CompletableFuture 모든 동작 완료 확인

public static void main(String[] args) throws ExecutionException, InterruptedException {
        final int num = 100;

        CompletableFuture cf1 = CompletableFuture.completedFuture(num)
                .thenApply(sNum -> {
                    System.out.println("first start");
                    return sNum + 100;
                }).thenAcceptAsync(aNum ->{
                    try {
                        Thread.sleep(2000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println("first end");
                });

        CompletableFuture cf2 = CompletableFuture.completedFuture(num)
                .thenApply(sNum -> {
                    System.out.println("second start");
                    return sNum;
                }).thenAcceptAsync(aNum ->{
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println("second end");
                });

        CompletableFuture.allOf(cf1, cf2).join();
        System.out.println("all end");
    }