用编译原理方法计算表达式的值,例如(2+3)*84+3这样的复杂表达式 深入体现了面向对象的方法,代码可以很容易进行overwrite-with compiler theory calculated the value of the expression. For example, (2)* 84 3 such a complex expression reflects the depth of object-oriented methods, code can easily overwri