README.md

Automaton

This is a simple library for simulating deterministic finite automata (DFA).

Examples

Let's go ahead and create a simple Automaton. Consider the following example.

First, let's define the States of our Automaton.

State qFinal = new State();

State q2 = new State(new Transition(qFinal, '0'));
State q1 = new State(new Transition(qFinal, '1'));

State qInitial = new State(
        new Transition(q1, '0'),
        new Transition(q2, '1')
);

qInitial.addSelfReference('2', '3');

Note that a reference to a State itself cannot be readily established when instantiating it, because at that stage the State is not yet defined. To get around that, we can use the State's addSelfReference() method.

Now we can create the Automaton itself. Observe that we only need to pass it our initial State.

Automaton automaton = new Automaton(qInitial);

Hurray! We have successfully set up our Automaton. The only thing left is testing it. Let us write a simple test function to do that for us.

private List<Boolean> test(String... cases) {
    return Stream.of(cases).map(automaton::canAccept).collect(Collectors.toList());
}

Calling our test() method with the arguments "222333210", "01", "33310", "23320210" yields the following results:

true

true

true

false

Which is exactly how it should be. Congratulations! You are now ready to use this library in whichever way you see fit :).

Complete example

public class Test {

    public static void main(String[] args) {
        Test t = new Test();

        Automaton automaton = t.setup();

        List<Boolean> results = t.test(automaton, "222333210", "01", "33310", "23320210");

        results.forEach(System.out::println);
    }

    private Automaton setup() {
        State qFinal = new State((Transition) null);

        State q2 = new State(new Transition(qFinal, '0'));
        State q1 = new State(new Transition(qFinal, '1'));

        State qInitial = new State(
                new Transition(q1, '0'),
                new Transition(q2, '1')
        );

        qInitial.addSelfReference('2', '3');

        return new Automaton(qInitial);
    }

    private List<Boolean> test(Automaton automaton, String... cases) {
        return Stream.of(cases).map(automaton::canAccept).collect(Collectors.toList());
    }
}