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I want to create a generic function that takes any Map & a String key, if the key is not present in the map, then it should create a new instance of the Value Type (which is passed) & put it in the map & then return it. Here is my implementation public <T> T getValueFromMap(Map<String, T> map, String key, Class<T> valueClass){ T value = map.get(key); if (value == null){ try { value = valueClass.newInstance(); } catch (InstantiationException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IllegalAccessException e) { // TODO Auto-generated catch block e.printStackTrace(); } map.put(key, value); } return value; } It works if I use it with a normal (not generic) List as the value type, Map<String,List> myMap; List value = getValueFromMap(myMap, "aKey", List.class) //works but not with generic type lists Map<String,List<String>> myMap; List<String> value = getValueFromMap(myMap, "aKey", List.class) //does not work Also if I try to make Map<String, T> map parameter generic by changing it to Map<String, T<?>> it complains that the type T is not generic; it cannot be parameterized with arguments <?> Can the generic parameters be themselves made generic? Is there any way to create function with above mentioned requirements? ~Update Thanks for all the insightful answers everyone. I have verified that the accepted solution works for any value type with this code Map<String, Map<String, List<String>>> outer = new HashMap<String, Map<String,List<String>>>(); Map<String, List<String>> inner =

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