code: public static String andWith(final String str, final String boolString) {
      if (Strings.isEmpty(str)) { return null; }
      if (Strings.isEmpty(boolString)) { return str; }
      if (str.length() < boolString.length()) { return str; }
      final StringBuilder buffer = new StringBuilder(str);
      for (int i = 0; i < buffer.length(); i++) {
        if (boolString.charAt(i) == '0') {
          buffer.setCharAt(i, '0');
        }
      }
      return buffer.toString();
    }
docs: 将一个字符串，按照boolString的形式进行变化. 如果boolString[i]!=0则保留str[i],否则置0
  
  @param str a {@link java.lang.String} object.
  @param boolString a {@link java.lang.String} object.
  @return a {@link java.lang.String} object.