Math Expression Evaluation With RegEx and Finite State Machines

The Context I created a Java application that evaluates simple mathematical expressions that the user inputs. The expressions were parsed with regular expressions like so:

RegEx to FSM I have created the finite state machine for A to the left, the first regex statement (the one directly after return ). Each arrow that doesn’t have a condition is an implied “anything else” (or “^[[-]*]” in S 0 ’s case). The other regular expressions are very similar, they just have dots included. Figure A.

RegEx to FSM I created one finite state machine based on the whole return statement by calling each expression A, B, C, D, E, F, G, H, and I respectively: