Java8:处理文件的供应商抛出“流已经被操作或关闭”

Question

java.lang.IllegalStateException: stream has already been operated upon or closed

• java-stream已被操作或关闭

与供应商合作可以解决此问题。

所以我当前的代码如下：

    try (Stream<String> stream =  Files.lines(Paths.get(fileName)) ) {

        Supplier<Stream<String>> supplier = () -> stream;

        logger.info("A");
        logger.info("ABC {}", supplier.get().findFirst().get());
        logger.info("B");
        logger.info("XYZ {}", supplier.get().skip(1050).findFirst().get());
        logger.info("C");

        assertThat(supplier.get().count(), is(1051));

    }
    catch (IOException e) {
        logger.error("{}", e.getMessage());
    }

   try (Stream<String> stream =  Files.lines(Paths.get(fileName)) ) {

        Supplier<Stream<String>> supplier = () -> stream.collect(Collectors.toList()).stream();

        logger.info("A");
        logger.info("ABC {}", supplier.get().findFirst().get());
        logger.info("B");
        logger.info("XYZ {}", supplier.get().skip(1050).findFirst().get());
        logger.info("C");

        assertThat(supplier.get().count(), is(1051));

    }

相同的错误信息。

Answer 1

供应商并不神奇，您仍然需要一直从该供应商提供一个新的流。

所以你可以做：

Supplier<Stream<String>> supplier = () -> Files.lines(Paths.get(fileName));

但这意味着要一直阅读文件。您可以将所有行读入单个列表，将其存储在内存中，并将其存储在流中。

List<String> allLines = Files.readAllLines(Paths.get(fileName));

Supplier<Stream<String>> supplier = () -> allLines.stream();

 Supplier<Stream<String>> streamSupplier = () -> Stream.of(array);