code: public static boolean isFormula(String formula) {
          while (FORMULA_REPLACE_PATTERN.matcher(formula).find()) {
              formula = formula.replaceAll(CALCULATION_FORMULA_PATTERN_STRING, "0");
          }
          return CALCULATION_FORMULA_PATTERN.matcher(formula).matches();
      }
docs: 验证计算式是否合法
  
  @param formula 计算式
  
  @return {@link Boolean}