如何使用 for 迭代 Java 中的流？
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How do I iterate over a stream in Java using for?
提问by ytoledano
I have this code:
我有这个代码：
List<String> strings = Arrays.asList("a", "b", "cc");
for (String s : strings) {
if (s.length() == 2)
System.out.println(s);
}
I want to write it using a filter and a lambda:
我想使用过滤器和 lambda 来编写它：
for (String s : strings.stream().filter(s->s.length() == 2)) {
System.out.println(s);
}
I get Can only iterate over an array or an instance of java.lang.Iterable.
我明白了Can only iterate over an array or an instance of java.lang.Iterable。
I try:
我尝试：
for (String s : strings.stream().filter(s->s.length() == 2).iterator()) {
System.out.println(s);
}
And I get the same error. Is this even possible? I would really prefer not to do stream.forEach() and pass a consumer.
我得到了同样的错误。这甚至可能吗？我真的不想做 stream.forEach() 并传递消费者。
Edit: it's important to me not to copy the elements.
编辑：对我来说不要复制元素很重要。
采纳答案by assylias
You need an iterable to be able to use a for-each loop, for example a collection or an array:
您需要一个可迭代对象才能使用 for-each 循环，例如集合或数组：
for (String s : strings.stream().filter(s->s.length() == 2).toArray(String[]::new)) {
Alternatively, you could completely get rid of the for loop:
或者，您可以完全摆脱 for 循环：
strings.stream().filter(s->s.length() == 2).forEach(System.out::println);
You mention you don't want to refactor your for loop but you could extract its body in another method:
你提到你不想重构你的 for 循环，但你可以用另一种方法提取它的主体：
strings.stream().filter(s->s.length() == 2).forEach(this::process);
private void process(String s) {
//body of the for loop
}
