DeterministicFiniteAutomaton.java

import java.util.HashSet;
import java.util.Scanner;

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
/**
 *
 * @author omar
 */
public class Dfa {

    public static void main(String[] args) {
        HashSet<String> mAcceptedStates = new HashSet();
        mAcceptedStates.add("s1");
        mAcceptedStates.add("s2");
        mAcceptedStates.add("s4");
        // fill the table
        String table[][] = new String[][]{{"s1", "s2", "s4"}, {"s2", "s2", "s3"}, {"s3", "s2", "s3"}, {"s4", "s5", "s4"}, {"s5", "s5", "s4"}};
        Scanner in = new Scanner(System.in);
        String word = in.next();
        int start = 0;
        int from = 0, to = 0;

        for (int i = 0; i < word.length(); i++) {
            char c = word.charAt(i);
            from = start;
            to = c == 'a' ? 1 : 2;

            System.out.print("s" + (from + 1) + " --" + c + "-> " + table[from][to] + "  ");
            if (i % 2 == 0 && i != 0) {
                System.out.println("");
            }

            start = Integer.parseInt(table[from][to].charAt(1) + "") - 1;

        }
        String endState = table[from][to];
        System.out.println("");
        System.out.println("result " + endState);
        System.out.println(mAcceptedStates.contains(table[from][to]) ? " yes " + endState + " is accepted state" : "no " + endState + " is not accepted state ");

    }

}