HashMap<String, String> map = new HashMap<String, String>(){
    @Override
    public boolean equals(Object o) {
        // TODO comparison here
        return super.equals(o);
    }
};
map.equals(new HashMap<String, String>());

public class NewHashMap<K,V> extends HashMap<K, V>

@Override
public boolean equals(Object o) {
    // Your code
}

public class HashMapComparator {
    boolean static areMapsEqual(HashMap<String, String> aMap, HashMap<String, String> bMap) {
        ....
    }
}

boolean mapsAreEqual = HashMapComparator.areMapsEqual(firstMap, secondMap);