public static String prefixString(int indentFlag, String tail) {
    StringBuilder sb = new StringBuilder();
    for (int index = 0; index < indentFlag; index++) {
      sb.append("  ");
    }
    int len = sb.length();
    return sb.replace(len - tail.length(), len, tail).toString();
  }
@param indentFlag
@param tail
         help to generate correct indent with a specific tail
@return
common/src/java/org/apache/hadoop/hive/common/jsonexplain/DagJsonParser.java