In this chapter, we covered the State design pattern. The State pattern is an implementation of one or more finite-state machines (in short, state machines) used to solve a particular Software Engineering problem.

A state machine is an abstract machine with two main components: states and transitions. A state is the current status of a system. A state machine can have only one active state at any point in time. A transition is a switch from the current state to a new state. It is normal to execute one or more actions before or after a transition occurs. State machines can be represented visually using state diagrams.

State machines are used to solve many computational and non-computational problems. Some of them are traffic lights, parking meters, hardware design, programming language parsing, and so forth. We saw how a snack vending machine relates to the way a state machine works.

Modern software offers libraries/modules to make the implementation and usage of state machines easier...