et Voila the challenge is complited B|

Main.java

import java.util.Objects;

public class Main {

    public static void main(String[] args) {
        System.out.println(countCouple("abc", "axc"));
    }

    public static int countCouple(String firstWord, String secondWord) {
        int count = 0;


        for (int i = 0; i < (firstWord.length() - 1); i++) {

            String firstCouple = String.valueOf(firstWord.charAt(i)) + String.valueOf(firstWord.charAt(i + 1));

            for (int j = 0; j < (secondWord.length() - 1); j++) {

                String secondCouple = String.valueOf(secondWord.charAt(j)) + String.valueOf(secondWord.charAt(j + 1));

                if (Objects.equals(firstCouple, secondCouple)) {
                    count++;
                }

            }
        }

        return count;
    }


}