Magic exchangeable words

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class HomeworksTests {

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        String string1 = scan.nextLine();
        String string2 = scan.nextLine();
        boolean result = exchange(string1, string2);
        System.out.println(result);
    }
    public static boolean exchange(String string1, String string2) {

        HashMap<Character, Character> dictionary = new HashMap<>();

        if (string1.length() != string2.length()) {
            System.out.println("Incorrect format!");
            return false;
        } else {
            for (int i = 0; i < string1.length(); i++) {

                        dictionary.put(string1.charAt(i), string2.charAt(i));
            }
            for (int i = 0; i < string1.length(); i++) {
                if (dictionary.containsKey(string1.charAt(i))) {
                    if (dictionary.get(string1.charAt(i)) != string2.charAt(i)) {
                        return false;
                    }
                } else {
                    return false;
                }
            }
        }
        return true;
    }
}