Hi basically I need help java and my program is an calculator which must be able to calculate arbitrary expressions like for example (5.0+8.1)*(2.0). My program works fine it does basic things like calling upon classes etc it's just I don't know how to do the arbitrary expressions. My calculator so far does all the basic things such as addition/subtraction/multiplication and division, but it must do arbitrary expressions.

I don't have to do system.input it just a program that tests calculations.

Any suggestions on how I can link them up?