docs: public static String escape(String str) {
  		if (StrUtil.isEmpty(str)) {
  			return str;
  		}
  
  		final int len = str.length();
  		final StringBuilder builder = new StringBuilder(len);
  		char c;
  		for (int i = 0; i < len; i++) {
  			c = str.charAt(i);
  			builder.append(escape(c));
  		}
  		return builder.toString();
  	}