将循环(while和for)转换为流 [英] Convert an loop (while and for) to stream

问题描述

我已经开始使用Java 8，并尝试将代码中的某些循环和旧语法转换为lambda和流.

I have started working with Java 8 and trying to convert some loops and old syntax in my code to lambdas and streams.

因此，例如，我试图在while和for循环中将其转换为流，但我做得不正确:

So for example, I'm trying to convert this while and for loop to stream, but I'm not getting it right:

List<String> list = new ArrayList<>();
if (!oldList.isEmpty()) {// old is a List<String>
    Iterator<String> itr = oldList.iterator();
    while (itr.hasNext()) {
        String line = (String) itr.next();
        for (Map.Entry<String, String> entry : map.entrySet()) {
            if (line.startsWith(entry.getKey())) {
         String newline = line.replace(entry.getKey(),entry.getValue());
                list.add(newline);
            }
        }
    }
}

我想知道是否可以将上述示例转换为单个流，其中for循环中有一个while循环.

I wanted to know if it's possible to convert the above example to a single stream where there is a while loop inside of a for loop.

推荐答案

如上所述，在此处使用流并不会真正增加价值，因为它使代码更难于阅读/理解.我知道您正在做更多的学习活动.话虽这么说，做这样的事情是一种功能性更强的方法，因为它没有从流本身内部添加到列表中的副作用:

As was stated above, using streams here doesn't really add value since it makes the code harder to read/understand. I get that you're doing it more as a learning exercise. That being said, doing something like this is a slightly more functional-style approach as it doesn't have a side effect of adding to the list from within the stream itself:

list = oldList.stream().flatMap(line->
            map.entrySet().stream()
                    .filter(e->line.startsWith(e.getKey()))
                    .map(filteredEntry->line.replace(filteredEntry.getKey(),filteredEntry.getValue()))
        ).collect(Collectors.toList());

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