java - How to dynamically change the document structure, merge into an array from a scalar value? -

i have collection of documents:

{"name":1,"b":3,"c":3} {"name":1,"b":3,"c":5} {"name":1,"b":3,"c":6} {"name":2,"b":6,"c":6} {"name":2,"b":6,"c":7} {"name":2,"b":6,"c":3} {"name":3,"b":2,"c":3} {"name":4,"b":2,"c":3} 

i merge collection following result:

{"name":1,"b":3,"c":[3,5,6]} {"name":2,"b":6,"c":[6,7,3]} {"name":3,"b":2,"c":3} {"name":4,"b":2,"c":3} 

which means eliminating duplicate documents , save c fields array. c array.

notes: first(e.g. "name") , second(e.g"b") fields unique per document.

while (cursor.hasnext()) {        dbobject currentobject = cursor.next();        string currentname = (string)currentobject.get("name");         if (currentname.equals(previousname) && !previousname.equals(""))         {             // should write here              collection.remove(previousobject);         }         previousobject = currentobject;         previousname = (string)previousobject.get("name");     } 

you can hold map of names , dbobjects , push value progress, this:

    map<string,dbobject> names = new hashmap<string, dbobject>();     while (cursor.hasnext()) {         dbobject currentobject = cursor.next();         string currentname = (string) currentobject.get("name");         dbobject o = names.get(currentname);         if (o!=null) { //means have it.             integer c = (integer) currentobject.get("c");             collection.remove(currentobject);             collection.update(o,new basicdbobject("$push",new basicdbobject("c",c)));         }else {             names.put(currentname,currentobject);         }     }