Hashmap containKey() method check

Question

When I call containsKey(value) it returns false when the key is in the map. I would appreciate it if someone could check my code!

I have already tried printing out they key and hashmap toString method and they Key is in the map.

    HashMap<IdentifierInterface, T> hm = new HashMap<IdentifierInterface, T>();

    public T getMemory(String v) {

        if(hm.containsKey(v)){

            return hm.get(v);
        }

        return null;
    }

Hashcode and Equals methods in IdentifierInterface:

public int hashCode() {
    return identifier.toString().hashCode();
}


public boolean equals(Object toCompare) {
    if (toCompare instanceof Identifier) {
        if (toCompare.hashCode() == this.hashCode()) {
            return true;
        }
    }
    return false;
}

The expected result is true and actual is false in getMemory().

Answer 1

The HashMap keys are of type IdentifierInterface, but you're calling containsKey(String).

In your equals() you however use instanceof Identifier which will always return false when a String is passed in.

So turn your String into an IdentifierInterface (or make the keys Strings instead).