使用Java扫描仪和矢量类的简单计算器

I am trying to create a simple calculator that calculates according to precedence. The method is passed a string(expression) that must be solved for. The way I am doing it is first parsing the string into two vectors, one holding the numbers and the other holding the operands. After I have successfully parsed the string, I then calculate and return the answer. I am getting a java.util.InputMismatchException from the scanner class I am using. Here is my code:I am trying to create a simple calculator that