几种读取文件方式的性能测试

/**
* 随机读取文件内容
* 
* @param fileName
*/
public static String readFileByRandomAccess(String path) {
  StringBuffer sb = new StringBuffer();
  RandomAccessFile randomFile = null;
  try {
    // 打开一个随机访问文件流，按只读方式
    randomFile = new RandomAccessFile(path, "rw");
    byte[] bytes = new byte[1024];
    int byteread = 0;
    while ((byteread = randomFile.read(bytes)) != -1) {
      // System.out.write(bytes, 0, byteread);
      sb.append(new String(bytes, 0, byteread));
    }
  } catch (IOException e) {
    e.printStackTrace();
  } finally {
    if (randomFile != null) {
      try {
        randomFile.close();
      } catch (IOException e1) {
      }
    }
  }
  return sb.toString();
}

/**
* 以行为单位读取文件，常用于读面向行的格式化文件
* 
* @param fileName
*/
public static String readFileByLines(String path) {
  StringBuffer sb = new StringBuffer();
  BufferedReader reader = null;
  try {
    reader = new BufferedReader(new FileReader(path));
    String tempString = null;
    while ((tempString = reader.readLine()) != null) {
    sb.append(tempString).append(System.getProperty("line.separator"));// 显示行号
    }
  } catch (IOException e) {
    e.printStackTrace();
  } finally {
    try {
      if (reader != null) {
        reader.close();
      }
    } catch (IOException e) {
      System.err.println("流关闭失败");
    }
  }
  return sb.toString();
}

/**
* 使用Java.nio ByteBuffer字节将一个文件输出
* 
* @param filePath
*/
public static String readFileByBybeBuffer(String path) {
  StringBuffer sb = new StringBuffer();
  FileInputStream in = null;
  FileOutputStream out = null;
  try {
    // 获取源文件和目标文件的输入输出流
    in = new FileInputStream(path);
    // 获取输入输出通道
    FileChannel fcIn = in.getChannel();
    ByteBuffer buffer = ByteBuffer.allocate(1024);
    CharBuffer charBuffer = null;
    Charset charset = Charset.forName("UTF-8");
    CharsetDecoder decoder = charset.newDecoder();
    while (true) {
      // clear方法重设缓冲区，使它可以接受读入的数据
      buffer.clear();
      // 从输入通道中将数据读到缓冲区
      int r = fcIn.read(buffer);
      if (r == -1) {
        break;
      }
      charBuffer = decoder.decode(buffer);
      // flip方法让缓冲区可以将新读入的数据写入另一个通道
      buffer.flip();
      sb.append(charBuffer.toString());
    }
  } catch (Exception e) {
    e.printStackTrace();
  } finally {
    try {
      if (in != null && out != null) {
        in.close();
        out.close();
      }
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
  //System.out.println(sb.toString());
  return sb.toString();
}

/**
* 通过scanner的方式读取文件
* 
* @param fileName
* @return
*/
public static String readByScanner(String path) {
  StringBuffer sb = new StringBuffer();
  Scanner s = null;
  try {
    File f = new File(path);
      s = new Scanner(f);
      while (s.hasNext()) {
      sb.append(s.next());
    }
  } catch (FileNotFoundException e) {
    e.printStackTrace();
  } finally {
    if(s!=null)s.close();
  }
  return sb.toString();
}

String fileName="Z:\\flume\\flume\\conf\\ErrLog";
long t1=OperateUtil.getTime();
OperateUtil.readByScanner(fileName);
long t2=OperateUtil.getTime();
OperateUtil.readFileByBybeBuffer(fileName);
long t3=OperateUtil.getTime();
OperateUtil.readFileByLines(fileName);
long t4=OperateUtil.getTime();
OperateUtil.readFileByRandomAccess(fileName);
long t5=OperateUtil.getTime();
    
System.out.println("readByScanner:"+(t2-t1));
System.out.println("readFileByBybeBuffer:"+(t3-t2));
System.out.println("readFileByLines:"+(t4-t3));
System.out.println("readFileByRandomAccess:"+(t5-t4));
ErrLog的文件大小是65M。

readByScanner:6180
readFileByBybeBuffer:171
readFileByLines:468
readFileByRandomAccess:531