Most efficient way to access 2D Maps (Maps of Maps) in Java? -

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i'm implementing weightedslopeone prediciton algorithm recommender system , @ point in code need have 2 2d maps, 1 map<integer, map<integer, integer>> , 1 map<integer, map<integer, double>>

as can understand accessing these , assigning values cumbersome procedure:

//the following 20 lines 1 line in python. sigh... hashmap<integer, integer> freqsforitem1 = frequencies.get(curitemid); //see if have value curitemid if (freqsforitem1 == null) {     freqsforitem1 = new hashmap<integer, integer>();     freqsforitem1.put(curitemid_2, 1);     frequencies.put(curitemid, freqsforitem1); } else {//see if have value curitemid+curitemid_2     integer freqforitem1item2 = freqsforitem1.get(curitemid_2);     if (freqforitem1item2 == null) {         //if don't have value item1+item2 put 1         freqsforitem1.put(curitemid_2, 1);     }     else {//we have value curitemid+curitemid_2         //so increment         freqsforitem1.put(curitemid_2, freqforitem1item2 + 1);     } }

so should using here instead of map<k1, map<k2, v>>, or if there no better data structure available better way access , change values of such map?

instead of using map of maps, can create new, immutable class (with properly implemented equals() , hashcode() methods!) stores 2 integer keys, , use that key simpler map.

class mykey {     int first;     int second;     // etc... }  map<mykey, integer> freqs = new hashmap<mykey, integer();

this simplify accessing & assigning values, , moreso if decide need make key more complex.


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