java多线程转换文件格式

private static final int THREAD_COUNT = 4; // 线程数
    private static final int BUFFER_SIZE = 1024; // 缓冲区大小

    /**
     * 多线程读取文件，转换文件编码格式 4线程 1Mb缓存
     *
     * @param inputFile     输入文件 String input = "E:/02code/web/test.txt";
     * @param sourceCharset 源文件编码 String output = "E:/02code/web/tes1t.txt";
     * @param outputFile    输出文件 String sourceCharset = "GBK";
     * @param targetCharset 目标文件编码 String targetCharset = "UTF-8";
     */
    private static void conversionFileEncodingFormat(File inputFile, String sourceCharset, File outputFile, String targetCharset) throws InterruptedException, IOException, ExecutionException {
        long fileSize = inputFile.length();
        long chunkSize = fileSize / THREAD_COUNT;

        ExecutorService executor = Executors.newFixedThreadPool(THREAD_COUNT);
        List<Future<File>> futures = new ArrayList<>();

        for (int i = 0; i < THREAD_COUNT; i++) {
            long start = i * chunkSize;
            long end = (i == THREAD_COUNT - 1) ? fileSize : (start + chunkSize);
            futures.add(executor.submit(new FileReadTask(inputFile, start, end, i, sourceCharset, targetCharset)));
        }

        executor.shutdown();
        executor.awaitTermination(1, TimeUnit.HOURS);

        try (BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(outputFile))) {
            for (Future<File> future : futures) {
                File tempFile = future.get();
                try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream(tempFile))) {
                    byte[] buffer = new byte[BUFFER_SIZE];
                    int bytesRead;
                    while ((bytesRead = bis.read(buffer)) != -1) {
                        bos.write(buffer, 0, bytesRead);
                    }
                }
                tempFile.delete(); // 删除临时文件
            }
        }
    }

    static class FileReadTask implements Callable<File> {
        private final File inputFile;
        private final long start;
        private final long end;
        private final int index;
        /**
         * 源文件编码
         */
        private final String sourceCharset;
        /**
         * 目标文件编码
         */
        private final String targetCharset;

        public FileReadTask(File inputFile, long start, long end, int index, String sourceCharset, String targetCharset) {
            this.inputFile = inputFile;
            this.start = start;
            this.end = end;
            this.index = index;
            this.sourceCharset = sourceCharset;
            this.targetCharset = targetCharset;
        }

        @Override
        public File call() throws Exception {
            File tempFile = new File("temp_" + index + ".txt");
            try (RandomAccessFile raf = new RandomAccessFile(inputFile, "r");
                 BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(tempFile), targetCharset))) {

                raf.seek(start);
                byte[] buffer = new byte[BUFFER_SIZE];
                long bytesToRead = end - start;
                while (bytesToRead > 0) {
                    int bytesRead = raf.read(buffer, 0, (int) Math.min(buffer.length, bytesToRead));
                    if (bytesRead == -1) break;
                    String chunk = new String(buffer, 0, bytesRead, sourceCharset); // 假设原文件编码为 ISO_8859_1
                    writer.write(chunk);
                    bytesToRead -= bytesRead;
                }
            }
            return tempFile;
        }
    }