java快速读取文本文件最后一行数据内容

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public static void main(String[] args) throws Exception {  
  File file = new File("E:/a.txt"); // 100M  
  long start = System.currentTimeMillis();  
  String lastLine = readLastLine(file, "gbk");  
  long delt = System.currentTimeMillis() - start;  
  System.out.println(lastLine);  
  System.out.println("读取时间(毫秒):" + delt);  
  
  file = new File("E:/b.txt");// 仅一行文字  
  start = System.currentTimeMillis();  
  lastLine = readLastLine(file, "gbk");  
  delt = System.currentTimeMillis() - start;  
  System.out.println(lastLine);  
  System.out.println("读取时间(毫秒):" + delt);  
}  
  
public static String readLastLine(File file, String charset) throws IOException {  
  if (!file.exists() || file.isDirectory() || !file.canRead()) {  
    return null;  
  }  
  RandomAccessFile raf = null;  
  try {  
    raf = new RandomAccessFile(file, "r");  
    long len = raf.length();  
    if (len == 0L) {  
      return "";  
    } else {  
      long pos = len - 1;  
      while (pos > 0) {  
        pos--;  
        raf.seek(pos);  
        if (raf.readByte() == '\n') {  
          break;  
        }  
      }  
      if (pos == 0) {  
        raf.seek(0);  
      }  
      byte[] bytes = new byte[(int) (len - pos)];  
      raf.read(bytes);  
      if (charset == null) {  
        return new String(bytes);  
      } else {  
        return new String(bytes, charset);  
      }  
    }  
  } catch (FileNotFoundException e) {  
  } finally {  
    if (raf != null) {  
      try {  
        raf.close();  
      } catch (Exception e2) {  
      }  
    }  
  }  
  return null;  
}