Switching states means that a pointer is followed and the current state is replaced with the state that the arrow points to.
Finally, when the loop is over, we check if the automaton “can stop” (the current state is double-circled) and that input has been exhausted.
In a nutshell, such a machine declares states and ways of getting from one state to another.
As a quick example, we can also validate input without an external, third-party library.Validating input received from the user to maintain data integrity is an important part of application logic.Validation of data can take place at different layers in even the simplest of applications, as shown in Developing a Simple Facelets Application.Functional Java has a useful Validation class, that may be a little daunting to new users at first, but is actually both quite simple and straight forward to use and extremely powerful. The Validation class takes two generic type parameters, one for the Error type and one for the Success type. The Functional Java Validation class turns out to be very useful when we have multiple Validations to perform.So let’s add another one A Semigroup is simply a type that wraps Functional Java’s version of a singly typed Bi Function (that also obeys some laws, but we won’t worry about that for now).
This class is used both to validate user input, and act as a 'transfer object' when interacting with the database.