大神看看这道java题目，帮忙解决一下

Question

Consider an expression like E:"123 * x + 456 * y * 12 - 200 / z" which follows the rules:
· may contain operands: +,-,*,/
· may contain variables (like 'x')
· may contain constants (like '123')
· does not contain parenthesis.
Write a set of Java classes to parse and "compile" expressions like E. Once the expression is "compiled"
it should be able to evaluated against a Map which would contain the value for the
variables. For example the expression "x + 2*y" would result to7 when evaluated against [x ->1, y ->3].
By "compiled" we mean that if the expression is to be evaluated against 1m inputs, the work of parsing
the expression into a set of Java classes should only be done once.
You should write a set of unit tests to show that your implementation is correct.
This is an Object Oriented Programing exercise. Focus should be put on good use of OOP principles
(encapsulation, good level of abstraction, low amount of duplicated code, design easy to extend, etc..)
and design patterns if necessary.
We recommend to use Maven, but you may use any other tool providing that you give sufficient
instruction to execute your code.
You may use generic libraries like Apache Common or Google Guava but you may not use scripting
libraries like JEXL, ANTLR or Grammatica.

Answer 1

强烈建议,先翻译完再过来,