Rather than making a map of maps (Map<K1,Map<K2,V>>), I find it often easier to make a map that uses a composite key : Map<Key<K1, K2>, V>.

You could make a generic Key class for this, or make a dedicated class on a per case basis since sometimes this key makes sense business-wise : e.g. Buyer - Seller -> Contract.

Nevertheless, if you use a generic Key class (make sure equals() and hashCode() are implemented properly), you could still have use for a variant of your MapMap, that takes individual K1 and K2 objects and combines them into a key behind the scenes. But I think you'll find that a Key class with a static factory method is easy enough to use :

getting :

V value = map.get(key(k1, k2);

or putting :

map.put(key(k1, k2), value);

Rather than making a map of maps (Map<K1,Map<K2,V>>), I find it often easier to make a map that uses a composite key : Map<Key<K1, K2>, V>.

You could make a generic Key class for this, or make a dedicated class on a per case basis since sometimes this key makes sense business-wise : e.g. Buyer - Seller -> Contract.

Nevertheless, if you use a generic Key class (make sure equals() and hashCode() are implemented properly), you could still have use for a variant of your MapMap, that takes individual K1 and K2 objects and combines them into a key behind the scenes. But I think you'll find that a Key class with a static factory method is easy enough to use :

getting :

V value = map.get(key(k1, k2));

or putting :

map.put(key(k1, k2), value);

Rather than making a map of maps (Map<K1,Map<K2,V>>), I find it often easier to make a map that uses a composite key : Map<Key<K1, K2>, V>.

You could make a generic Key class for this, or make a dedicated class on a per case basis since sometimes this key makes sense business-wise : e.g. Buyer - Seller -> Contract.

Nevertheless, if you use a generic Key class (make sure equals() and hashCode() are implemented properly), you could still have use for a variant of your MapMap, that takes individual K1 and K2 objects and combines them into a key behind the scenes. But I think you'll find that a Key class with a static factory method is easy enough to use :

getting :

V value = map.get(key(k1, k2);

or putting :

map.put(key(k1, k2), value);

Rather than making a map of maps (Map<K1,Map<K2,V>>), I find it often easier to make a map that uses a composite key : Map<Key<K1, K2>, V>.

You could make a generic Key class for this, or make a dedicated class on a per case basis since sometimes this key makes sense business-wise : e.g. Buyer - Seller -> Contract.

Nevertheless, if you use a generic Key class (make sure equals() and hashCode() are implemented properly), you could still have use for a variant of your MapMap, that takes individual K1 and K2 objects and combines them into a key behind the scenes. But I think you'll find that a Key class with a static factory method is easy enough to use :

getting :

V value = map.get(key(k1, k2);

or putting :

map.put(key(k1, k2), value);