java 如何在java Stream中捕获拆分的字符串
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How to catch splitted string in java Stream
提问by Kaspar
So let's say that we have a string: "randomText1 randomText2" in an array, which is loaded into a Stream.
所以假设我们有一个字符串：“randomText1 randomText2”在一个数组中，它被加载到一个流中。
Now I go over all the lines in this stream, and I split every line at the space character.
现在我检查这个流中的所有行，并在空格字符处拆分每一行。
strings
.map(string -> string.split(" "))
.flatMap(Arrays::stream)
.collect(new MyClass(string1, string2));
How can I get the both sides of the string and do whatever I want with them from there on?
我怎样才能得到字符串的两边并从那里开始做我想做的任何事情？
From Oracle docs (Oracle doc link) I only managed to find some harder cases where one would be using a Map<>for instance. But I fail to fit their solutions to this more simpler problem of mine.
从 Oracle 文档（Oracle 文档链接）中，我只能找到一些更难的案例，Map<>例如，人们将使用 a 。但是我无法将他们的解决方案适合我这个更简单的问题。
回答by Holger
Using flatMapis not the right tool for the job. What you apparently want to do is
使用flatMap不是工作的正确工具。你显然想要做的是
strings.map(string -> string.split(" ", 2))
.map(array -> new MyClass(array[0], array[1]))
You may process the stream further by using .collect(Collectors.toList())to get a List<MyClass>or .findAny()to get a single MyClassinstance (if any).
您可以通过使用.collect(Collectors.toList())获取List<MyClass>或.findAny()获取单个MyClass实例（如果有）来进一步处理流。
Generally, streaming an array is only useful if you want to treat all elements uniformly, i.e. notif their position has a special meaning which has to be preserved for subsequent operations.
通常，流式传输数组仅在您想统一处理所有元素时才有用，即如果它们的位置具有特殊含义，必须为后续操作保留该含义，则无效。
And ifyou really want to create a flat stream of words or tokens, you shouldn't use the combination of String.splitand Arrays.streamas that will create and fill an unnecessary intermediate array. In this case use
而且，如果你真的想创造的词或令牌的扁平流，你不应该使用的组合String.split，并Arrays.stream为将创建并填写不必要的中间阵列。在这种情况下使用
strings.flatMap(Pattern.compile(" ")::splitAsStream)
回答by lbalazscs
It was an interesting challenge even if streams should not be used for such simple tasks. Here's the complete code:
即使不应该将流用于如此简单的任务，这也是一个有趣的挑战。这是完整的代码：
public class Example {
public static void main(String[] args) {
String[] strings = {"randomText1 randomText2"};
MyClass myClass = Arrays.stream(strings)
.map(string -> string.split(" "))
.flatMap(Arrays::stream)
.collect(new MyCollector());
System.out.println("myClass = " + myClass.toString());
}
}
class MyCollector implements Collector<String, List<String>, MyClass> {
@Override
public BiConsumer<List<String>, String> accumulator() {
return List::add;
}
@Override
public Supplier<List<String>> supplier() {
return ArrayList::new;
}
@Override
public BinaryOperator<List<String>> combiner() {
return (strings, strings2) -> {
strings.addAll(strings2);
return strings;
};
}
@Override
public Function<List<String>, MyClass> finisher() {
return strings -> new MyClass(strings.get(0), strings.get(1));
}
@Override
public Set<Characteristics> characteristics() {
return Collections.emptySet();
}
}
class MyClass {
String s1;
String s2;
public MyClass(String s1, String s2) {
this.s1 = s1;
this.s2 = s2;
}
@Override
public String toString() {
return "MyClass{" +
"s1='" + s1 + '\'' +
", s2='" + s2 + '\'' +
'}';
}
}
