DFA for All string of length at most five

These are the valid strings:

A string of length 0 – accept through q₀.
A string of length 1 – accept through q₁.
A string of length 2 – accept through q₂.
A string of length 3 – accept through q₃.
A string of length 4 – accept through q₄.
A string of length 5 – accept through q₅.

String of length > 5 should be rejected through a dead state or failure state. A failure state is designated as q₀.

Designing DFA step by step:

Step -1:

String length less than or equal to 5 are accept to length 0 is also accept. So “q₀” is also accepts.

Step -2:

String length of 1 is also accepted of ‘0’ or ‘1’. Create transition of input alphabet ‘1’ or ‘0’ from state “q₀” to state “q₁“.

Step -3:

After this length of string is 1 and 2 length is also accept. So, send input alphabet ‘0’ and ‘1’ from state “q₁” to state “q₂“.

Step -4:

Repeat the above step it gets the string length less than five. As less than five is the accept table so make the states “q₀, q₁, q₂, q₃, q₄, q₅” be the final state.

transition Diagram - All string of length at most five — Transition Diagram

Transition table of above DFA:

transition table - All string of length at most five — Transition Table

In the above table, -> represents the initial state and * represents the final state. In this post, the initial and final state is the same which is the final state.

Code:

Main.java

import java.util.Scanner;
public class less_than_5 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter the string");
        String str = sc.nextLine();

        stateA(str);
    }

    private static void stateA(String str) {

        if(str.length() <= 5){
            System.out.println("String Accepted");
        }
        else {
            if(str.charAt(0)=='0')
                stateB(str.substring(1));
            else
                stateB(str.substring(1));
        }
    }

    private static void stateB(String str) {

        if(str.length() == 0){
            System.out.println("String not accepted");
        }
        else {
            if(str.charAt(0)=='0')
                stateB(str.substring(1));
            else
                stateB(str.substring(1));
        }
    }
}

Output:

Enter the string
1010101
String not accepted