How to implement a HashMap in which key is an object of the class I created?

Question

Java

Good afternoon!
Can you please tell me how can I use an object of my own class as a key? It only comes to mind to do some unambiguous transformation of the value of the variables of the Location class. For example, define a toString() method and use a String as the HashMap key. But in this case, further use of entry.getKey() is difficult. I specified the toString() method in the code, but did not use it. Are there better ways to get out of this situation?

class Hero{
    // Описание класа
}
class Location{
    private int m;
    private int n;

    int getM() {
        return m;
    }
    int getN(){
        return n;
    }
    String toString(){
        return "" + m + n;
    }
}

public class Main {

    public static void main(String[] args) {

        HashMap<Location, Hero> map = new HashMap<>();
    }
}

Answer 1

It is necessary to consistently implement the equals and hashCode methods. Consistently, if equals returned true, then hashCode will return the same number. The converse is not necessarily true.