英文:
Is it possible use current stream functions inside stream function?
问题
例如，我有一些字符串。我想通过空格将它分割，然后筛选只有长度大于流计数的单词。请参考下面的代码：
Arrays.stream("一些重要的字符串".split(" "))
.filter(word -> word.length() > /*（如何在此获取流计数？）*/)
任务是在一行内完成它（不使用外部变量）。
英文:
For example I have some string. I want split it by space and then filter only words that have length that is greater than stream count. See code below
Arrays.stream("Some important string".split(" "))
.filter(word->word.length>([HOW GET HERE STREAM COUNT??]))
The task is do it in one line (without external variables)
答案1
得分: 1
这是一个hack，我强烈不建议使用，但你可以像这样做：
String[] result = Stream.<String[]>of("Some important strings to test".split(" "))
.flatMap(words -> Stream.of(words).filter(word -> word.length() > words.length))
.toArray(String[]::new);
System.out.println(Arrays.toString(result));
如果你只是简单地使用一个变量，代码会好得多：
String[] words = "Some important strings to test".split(" ");
String[] result = Stream.of(words)
.filter(word -> word.length() > words.length)
.toArray(String[]::new);
System.out.println(Arrays.toString(result));
两者的输出
[important, strings]
如果问题不是关于如何使用split()返回的数组，而实际上是字面上的问题**“如何获取流的数量”**，那么答案是你无法做到。
即使你可以访问流，也无法调用 count() 方法，因为那会消耗流并违反调用的目的。
英文:
This is a hack, and I would strongly discourage the use, but you can do it like this:
String[] result = Stream.<String[]>of("Some important strings to test".split(" "))
.flatMap(words -> Stream.of(words).filter(word -> word.length() > words.length))
.toArray(String[]::new);
System.out.println(Arrays.toString(result));
The code would be much better if you simply use a variable:
String[] words = "Some important strings to test".split(" ");
String[] result = Stream.of(words)
.filter(word -> word.length() > words.length)
.toArray(String[]::new);
System.out.println(Arrays.toString(result));
Output from both
[important, strings]
If the question is not about how to do it with an array returned by split(), but is actually the literal question "how to get stream count", then the answer is that you can't.
Even if you had access to the stream, you couldn't call count(), since that would consume the stream and defy the purpose of the call.
答案2
得分: 0
这不重要。
流只能被迭代一次，因此如果在流上调用.count()，就不能再调用.filter()。
下面是一个使用count()在表达式中的笨拙示例，用于对其进行filter()：
Stream.of(Arrays.stream("一些重要的字符串".split(" ")))
.map(s -> s.filter(x -> x.length() > s.count())).findAny().get().toArray();
这是可预测的结果：
Exception in thread "main" java.lang.IllegalStateException:
流已经被操作或关闭
在 java.util.stream.AbstractPipeline.<init>(AbstractPipeline.java:203)
英文:
It doesn't matter.
A stream can only be iterated over once, so if you call .count() on the stream you can no longer call .filter().
Here's a kludgy example that uses count() on the stream in the expression that filter()s it:
Stream.of(Arrays.stream("Some important string".split(" ")))
.map(s -> s.filter(x -> x.length() > s.count())).findAny().get().toArray();
And here's the predictable result:
Exception in thread "main" java.lang.IllegalStateException:
stream has already been operated upon or closed
at java.util.stream.AbstractPipeline.<init>(AbstractPipeline.java:203)
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论