public static void main(String[] args) {
    String orgin = "边叫边练，我喜欢叫练";
    String serach = "叫练";
    int index = indexOf(orgin,serach);
    System.out.println(index);
  }

/**
   * indexOf 算法原理
   * @param orgin 原始字符串 B = “边叫边练，我喜欢叫练”;
   * @param serachString 匹配字符串 A=“叫练”
   * @return int 下标
   */
public static int indexOf(String orgin,String serachString) {
  char[] chars = orgin.toCharArray();
  char[] sChars = serachString.toCharArray();
  //返回字符串下标
  int index = -1;
  //匹配字符串计数器，用于查询是否匹配到完整字符串
  int s_index = 0;
  //全局计数器，用于计算下标
  int move = 0;
  for (int i=0; i<chars.length; i++) {
    move++;
    //如果匹配到“叫”,继续向下开始匹配“练”
    if (chars[i] == sChars[s_index]) {
      s_index++;
      if(s_index == sChars.length) {
        index = move-sChars.length;
        break;
      }
    } else {
      s_index = 0;
    }
  }
  return index;
}

/**
   * @param orgin 原始字符串 B = “边叫边练，我喜欢叫练”;
   * @param serachString 匹配字符串 A=“叫练”
   **/
  function indexOf(orgin,serachString) {
    //返回字符串下标
    var index = -1;
    //匹配字符串计数器，用于查询是否匹配到完整字符串
    var s_index = 0;
    //全局计数器，用于计算下标
    var move = 0;
    for (var i=0; i<orgin.length; i++) {
      move++;
      //如果匹配到“叫”,继续向下开始匹配“练”
      if (orgin.substr(i,1) == serachString.substr(s_index,1)) {
        s_index++;
        if(s_index == serachString.length) {
          index = move-serachString.length;
          break;
        }
      } else {
        s_index = 0;
      }
    }
    return index;
  }

# indexOf 算法原理
# @param orgin 原始字符串 B = “边叫边练，我喜欢叫练”;
# @param serachString 匹配字符串 A=“叫练”
# @return int 下标
def index(orgin, serachString):
  # 返回字符串下标
  index = -1
  # 匹配字符串计数器，用于查询是否匹配到完整字符串
  s_index = 0
  # 全局计数器，用于计算下标
  move = 0
  for letter in enumerate(orgin):
    move = move + 1
    # 如果匹配到“叫”,继续向下开始匹配“练”
    if letter[1] == serachString[s_index]:
      s_index = s_index + 1
      if s_index == len(serachString):
        index = move - len(serachString)
        break
    else:
      s_index = 0;

  return index