Question

是否可以使用并行流和lambda执行下面的代码，因为它是一个更清晰的代码？我不知道该怎么做。

public static NavigableSet<String> getDistinctNavigableLowerCaseMakeNames(Loader loader) {
    String[] regions = {Japan, Germany, USA};
    final CountDownLatch latch = new CountDownLatch(regions.length);

    Set<Make> unique = new HashSet<>();
    for (Region region : regions) {
        EXECUTOR.submit(new Runnable() {
            @Override public void run() {
                List<Make> regionMakes = getVehicleMakesByRegion(region); //provides all the vehicles based on the region
                    unique.addAll(regionMakes);
                latch.countDown();
            }
        });
    }
    try {
        latch.await();
    } catch (InterruptedException ie) {
        Thread.currentThread().interrupt();
        throw new RuntimeException(ie);
    }

   return unique;
}

Make是一个由最终变量id，region和name组成的类。

Answer 1

据我了解，您希望找到区域列表的独特品牌。如果是这样的话：

Arrays.stream("Japan", "Germany", "USA").parallel()
    .map(loader::getVehicleMakesByRegion)
    .flatMap(List::stream)
    .map(Make::getName)
    .distinct()
    ...

如果Make.equals存在，那么您可以在distinct之前移动getName。更改getVehicleByRegion以返回Stream<Make>。

也可能有意义

Answer 2

这样的事情怎么样，看起来有点短：）

override func viewDidAppear(_ animated: Bool) {
        let query = PFQuery(className: "ProfilePictures")
        query.whereKey("user", equalTo: (PFUser.current()?.objectId!)! as String)
        query.findObjectsInBackground { (objects, error) in
            if let objectss = objects{
                if objectss.count != 0{
                    for object in objectss{
                        let imagePulled = object["ProfilePicture"] as! PFFile
                        imagePulled.getDataInBackground(block: { (data, error) in
                            if let downloadedImage = UIImage(data: data!){
                                self.imageHolder.image = downloadedImage
                            } else{
                                print(error)
                            }
                        })
                    }

                }
            }
            }
    }

请记住向Loader接口添加注释，指定实现必须是线程安全的。

JAVA 8 - Lambda和Streams替换ExecutorService

2 个答案: