code: protected String readHostsFile() throws IOException {
  		String path = this.getHostsPath();
  		BufferedReader reader = new BufferedReader(new FileReader(path));
  		StringBuilder sb = new StringBuilder();
  		String line;
  		while ((line = reader.readLine()) != null) {
  			sb.append(line).append("\n");
  		}
  		reader.close();
  		return sb.toString();
  	}
docs: 读取hosts文件内容.
  
  @return hosts文件内容
  @throws IOException