Java string to math equation [duplicate]

Answer 1

  static int eval(String infix) {        
        ScriptEngineManager mgr = new ScriptEngineManager();
        ScriptEngine engine = mgr.getEngineByName("JavaScript");    
        String stringResult;
        try {
            stringResult = engine.eval(infix).toString();
            double doubleResult = Double.parseDouble(stringResult);
            int result = (int) doubleResult;        
            return result;
        } catch (ScriptException ex) {
            Logger.getLogger(Ukol4a.class.getName()).log(Level.SEVERE, null, ex);
        }
        return(1);

    }