如何使用for迭代Java中的流？ [英] How do I iterate over a stream in Java using for?

问题描述

我有这段代码：

List<String> strings = Arrays.asList("a", "b", "cc");
for (String s : strings) {
    if (s.length() == 2)
        System.out.println(s);
}

我想用过滤器和lambda来编写它：

I want to write it using a filter and a lambda:

for (String s : strings.stream().filter(s->s.length() == 2)) {
    System.out.println(s);
}

我得到只能迭代数组或者java.lang.Iterable的实例。

我试试：

for (String s : strings.stream().filter(s->s.length() == 2).iterator()) {
    System.out.println(s);
}

我得到同样的错误。这有可能吗？我真的不想做stream.forEach（）并传递消费者。

And I get the same error. Is this even possible? I would really prefer not to do stream.forEach() and pass a consumer.

编辑：对我来说不要复制元素很重要。

it's important to me not to copy the elements.

推荐答案

你需要一个iterable才能使用for-each循环，例如一个集合或一个数组：

You need an iterable to be able to use a for-each loop, for example a collection or an array:

for (String s : strings.stream().filter(s->s.length() == 2).toArray(String[]::new)) {

或者，您可以完全摆脱for循环：

Alternatively, you could completely get rid of the for loop:

strings.stream().filter(s->s.length() == 2).forEach(System.out::println);

你提到你不想重构你的for循环但是你可以用另一种方法提取它的身体：

You mention you don't want to refactor your for loop but you could extract its body in another method:

strings.stream().filter(s->s.length() == 2).forEach(this::process);

private void process(String s) {
  //body of the for loop
}

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