Java实现grep时使用Stream的StringBuilder Collector程序挂起

我在入职培训项目中尝试用Java Stream实现grep功能，代码在IntelliJ中运行正常，但通过mvn clean package打包后，调用collect方法时程序出现挂起（省略了getter/setter及其他部分方法）。

JavaGrep类代码 #

class JavaGrep {
    public void process() throws IOException {
        Stream<Path> paths = listFiles(this.rootPath);
        logger.debug(this.outFile);
        paths.map(
            Path::toFile
        ).forEach(
            this::readLargeFile
        );
    }

    public Stream<Path> listFiles(String rootDir) {
        try {
            return Files.walk(Paths.get(rootDir)).filter(
                path -> !Files.isDirectory(path)
            );
        } catch (IOException e) {
            throw new RuntimeException("Error: IO Exception while reading root directory", e);
        }
    }

    void readLargeFile(File file)  {
        try(FileInputStream fis = new FileInputStream(file);) {
            byte[] buffer = new byte[CHUNK_SIZE]; // Buffer to hold 20MB chunks
            int counter = 1;
            long fileSize = Files.size(file.toPath());
            while (fis.read(buffer)!=-1) {
                logger.debug("Progress reading {} : {}", file.toPath(), Math.min((float) counter * (float)CHUNK_SIZE / (float)fileSize * 100.0, 100.0));
                counter++;
                String s = new String(buffer, StandardCharsets.ISO_8859_1);
                Stream<String> lines = Arrays.stream(s.split("\n"));
                String chunkContent = lines.filter(
                    this::containsPattern
                ).collect(
                    new StringBuilderCollector()
                );
                logger.debug("writing to file");
                this.writeToFile(chunkContent);
            }
        } catch (IOException e) {
            throw new RuntimeException("Error while reading file " + file.getPath(), e);
        }
    }

    public void writeToFile(String lines) {
        Path outFilePath = Paths.get(this.outFile);
        try(
            FileChannel fileChannel = FileChannel.open(outFilePath, StandardOpenOption.APPEND, StandardOpenOption.CREATE);
            FileLock lock = fileChannel.lock()
        ) {
            Files.write(outFilePath, lines.getBytes(StandardCharsets.ISO_8859_1), StandardOpenOption.APPEND);
        } catch (IOException e) {
            logger.error("error while opening atomic file channel for {}", outFilePath, e);
        }
    }
}

自定义Collector类代码 #

public class StringBuilderCollector implements Collector<String,StringBuilder,String> {

    StringBuilderCollector() {
    }

    @Override
    public Supplier<StringBuilder> supplier() {
        return StringBuilder::new;
    }

    @Override
    public BiConsumer<StringBuilder, String> accumulator() {
        return (sb, string) -> {
            sb.append(string);
            sb.append('\n');
        };
    }

    @Override
    public BinaryOperator<StringBuilder> combiner() {
        return (sb1, sb2) -> {
            sb1.append(sb2);
            return sb1;
        };
    }

    @Override
    public Function<StringBuilder, String> finisher() {
        return StringBuilder::toString;
    }

    @Override
    public Set<Characteristics> characteristics() {
        return Collections.emptySet();
    }
}

已尝试的操作 #

• 若输出文件不存在则创建它
• 打印/日志记录（accumulator工作正常，能输出所有预期行，因此过滤部分应该没问题，但combiner内的代码似乎从未运行）
• 将Files.walk放入try()块，但这引发了非法状态异常。ChatGPT表示调用collect时资源会自动关闭，因此我认为这不是问题

内容的提问来源于stack exchange，提问作者qwerty_99