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What is wrong with this instantiation :
Map<String, String, HashMap<String,String>> map = new HashMap<String, String, HashMap<String,String>>();
A
Map<K,V>is a mapping from keys of typeKto values of typeV. There are only 2 type parameters to a map.You attempted to define a map with 3 type parameters; this is not possible, and has nothing to do with the fact that you’re putting a
Mapinside aMap.A
Map<K1,Map<K2,V2>>works just fine.A
Map<X,Y,Z>does not.It’s possible that you need something like
Map< Pair<L,R>, Map<K,V> >. Java does not have genericPair<L,R>type, but see related questions below for solutions.Related questions
On pairs/tuples:
Pair<L,R>in Java?Pair<String, String>stored inHashMapnot retrieving key->value properlyOn nested maps: