java实现大文本文件拆分

public static void createBigFile() throws IOException {
 File file = new File("/Users/yangpeng/Documents/temp/big_file.csv");
 FileWriter fileWriter = new FileWriter(file);
 BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);
 String str = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa1";
 for (int i = 0; i < 1000000; i++) {
  bufferedWriter.write(str);
  bufferedWriter.newLine();
 }
 bufferedWriter.flush();
 bufferedWriter.close();
}

public static void splitFile(String filePath, int fileCount) throws IOException {
 FileInputStream fis = new FileInputStream(filePath);
 FileChannel inputChannel = fis.getChannel();
 final long fileSize = inputChannel.size();
 long average = fileSize / fileCount;//平均值
 long bufferSize = 200; //缓存块大小，自行调整
 ByteBuffer byteBuffer = ByteBuffer.allocate(Integer.valueOf(bufferSize + "")); // 申请一个缓存区
 long startPosition = 0; //子文件开始位置
 long endPosition = average < bufferSize ? 0 : average - bufferSize;//子文件结束位置
 for (int i = 0; i < fileCount; i++) {
  if (i + 1 != fileCount) {
   int read = inputChannel.read(byteBuffer, endPosition);// 读取数据
   readW:
   while (read != -1) {
    byteBuffer.flip();//切换读模式
    byte[] array = byteBuffer.array();
    for (int j = 0; j < array.length; j++) {
     byte b = array[j];
     if (b == 10 || b == 13) { //判断\n\r
      endPosition += j;
      break readW;
     }
    }
    endPosition += bufferSize;
    byteBuffer.clear(); //重置缓存块指针
    read = inputChannel.read(byteBuffer, endPosition);
   }
  }else{
   endPosition = fileSize; //最后一个文件直接指向文件末尾
  }

  FileOutputStream fos = new FileOutputStream(filePath + (i + 1));
  FileChannel outputChannel = fos.getChannel();
  inputChannel.transferTo(startPosition, endPosition - startPosition, outputChannel);//通道传输文件数据
  outputChannel.close();
  fos.close();
  startPosition = endPosition + 1;
  endPosition += average;
 }
 inputChannel.close();
 fis.close();

}

public static void main(String[] args) throws Exception {
 Scanner scanner = new Scanner(System.in);
 scanner.nextLine();
 long startTime = System.currentTimeMillis();
 splitFile("/Users/yangpeng/Documents/temp/big_file.csv",5);
 long endTime = System.currentTimeMillis();
 System.out.println("耗费时间： " + (endTime - startTime) + " ms");
 scanner.nextLine();
}