Java利用ScriptEngineManager对计算公式的支持

public static void main(String[] args) {         EngineManager manager = new  EngineManager();         Engine engine = manager.getEngineByName(" ");        try {            System.out.println(engine.eval("a*2".replace("a","2")));            System.out.println(engine.eval("a<2".replace("a","1")));        } catch ( Exception e) {            e.printStackTrace();        }    }