stream has already been operated upon or closed

아래와 같이 Stream을 재사용하는 경우에 발생함.

@Test
void test() {
	IntStream intStream = IntStream.rangeClosed(1, 100);

	intStream.forEach(System.out::println);
	intStream.forEach(System.out::println);
}

A Stream should be operated on (invoking an intermediate or terminal stream operation) only once. A Stream implementation may throw IllegalStateException if it detects that the Stream is being reused.

 

재사용이 필요한 곳에서는 Stream을 재생성한 후에 사용한다.

 

참고

https://www.baeldung.com/java-stream-operated-upon-or-closed-exception

"Stream has already been operated upon or closed" Exception in Java | Baeldung