Question

Given:

Object nestKey; Object nestedKey; Object nestedValue;  Map<T,Map<T,T>> nest; Map<T,T> nested;   

How is a mapping added to nested where:

nest.containsKey(nestKey) == true;

?

Or is there an existing library of collections that would be more effective?

Answer 1

You mean something like the following generic method?

static <U,V,W> W putNestedEntry(         Map<U,Map<V,W>> nest,         U nestKey,         V nestedKey,         W nestedValue) {     Map<V,W> nested = nest.get(nestKey);      if (nested == null)     {         nested = new HashMap<V,W>();         nest.put(nestKey, nested);     }      return nested.put(nestedKey, nestedValue);         }