code: public static Object calculateUseEval(String formula) throws ScriptException {
          ScriptEngineManager mgr = new ScriptEngineManager();
          ScriptEngine jsEngine = mgr.getEngineByName("JavaScript");
          return jsEngine.eval(formula);
      }
docs: 连续计算，可能导致数据失真
  
  @param formula 表达式
  
  @return {@link Double}
  
  @throws ScriptException 异常