How can I initialize List<List<Integer>> in Java?
I know List is an interface and I can use ArrayList or LinkedList to implement List<Integer> list = new ArrayList<Integer>(), but when I initialize List<List<Integer>> list = new ArrayList<ArrayList<Integer>>(); I get error incompatible types:
ArrayList<ArrayList<Integer>> cannot be converted to List<List<Integer>>.
So how can I proceed?
Use
List<List<Integer>> list = new ArrayList<List<Integer>>();
or since Java 1.7
List<List<Integer>> list = new ArrayList<>();
You can define it as List<List<Integer>> list = new ArrayList<List<Integer>>();.
Then while defining the inner List you can take care of initialising it as ArrayList<Integer>.
You can define it as List<List<Integer>> list = new LinkedList();
You can initialize this as
List<ArrayList<Integer>> list = new ArrayList<ArrayList<Integer>>();
Note that the inner List has to be an implementation of the List interface, e.g., ArrayList.
Since List is an interface, one can't have objects of the type List itself.
declarationrather than aninitailization. See this linke: stackoverflow.com/questions/6232986/…