I would say it depends on whether all the values with same key have a relationship that you want to address. So for example, do you often go through all elements with key X, or pass them to a function, and so on? Then it is more convenient to already have them in their separate … Read more
A std::map is an associative container, that allows you to have a unique key associated with your type value. For example, void someFunction() { typedef std::map<std::string, int> MapType; MapType myMap; // insertion myMap.insert(MapType::value_type(“test”, 42)); myMap.insert(MapType::value_type(“other-test”, 0)); // search auto it = myMap.find(“test”); if (it != myMap.end()) std::cout << “value for ” << it->first << ” … Read more
You are searching for a multimap, and indeed both commons-collections and Guava have several implementations for that. Multimaps allow for multiple keys by maintaining a collection of values per key, i.e. you can put a single object into the map, but you retrieve a collection. If you can use Java 5, I would prefer Guava’s … Read more
If you’re using .NET 3.5, use the Lookup class. EDIT: You generally create a Lookup using Enumerable.ToLookup. This does assume that you don’t need to change it afterwards – but I typically find that’s good enough. If that doesn’t work for you, I don’t think there’s anything in the framework which will help – and … Read more