Java8-once流被使用和操作，给出了错误，但在另一种情况下，它不是

Question

List<String> title = Arrays.asList("Java8", "In", "Action");
        Stream<String> s = title.stream();
        s.forEach(System.out::println);
        s.forEach(System.out::println); // THIS WILL GIVE ERROR - streams has been already operated and closed.

Java8
In
Action
Exception in thread "main" java.lang.IllegalStateException: stream has already been operated upon or closed
    at java.util.stream.AbstractPipeline.sourceStageSpliterator(Unknown Source)
    at java.util.stream.ReferencePipeline$Head.forEach(Unknown Source)
    at com.test.Java8InAction.CH4.TraversableOnlyOnce.main(TraversableOnlyOnce.java:12)

// Filtering unique elements
List<Integer> numbers = Arrays.asList(1, 2, 1, 3, 3, 2, 4);
numbers.stream().forEach(System.out::println);
numbers.stream().filter(n -> n % 2 == 0).distinct().forEach(System.out::println);
numbers.stream().filter(n -> n % 2 == 0).forEach(System.out::println);

在这里我也操作了流并关闭了终端操作，那为什么我没有得到任何错误？

Answer 1

foreach是终端操作。

终端操作完成后，流流水线被认为已消耗，不能再使用；

https://docs.oracle.com/javase/8/docs/api/java/util/stream/package-summary.html