I want to create a 2D array that each cell is an ArrayList!
I consider this defintions, but I can not add anything to them are these defintions true?!
ArrayList<ArrayList<String>> table = new ArrayList<ArrayList<String>>();
or
ArrayList[][] table = new ArrayList[10][10];
//table.add??????
Please help me
I want to create a 2D array that each cell is an ArrayList!
If you want to create a 2D array of ArrayList.Then you can do this :
ArrayList[][] table = new ArrayList[10][10];
table[0][0] = new ArrayList(); // add another ArrayList object to [0,0]
table[0][0].add(); // add object to that ArrayList
arrayListObject is not an ArrayList object.
unchecked call to add(e) as a member of the raw type that the datatype is not specified for the inner arraylist, how to do that ?The best way is to use a List within a List:
List<List<String>> listOfLists = new ArrayList<List<String>>();
1st of all, when you declare a variable in java, you should declare it using Interfaces even if you specify the implementation when instantiating it
ArrayList<ArrayList<String>> listOfLists = new ArrayList<ArrayList<String>>();
should be written
List<List<String>> listOfLists = new ArrayList<List<String>>(size);
Then you will have to instantiate all columns of your 2d array
for(int i = 0; i < size; i++) {
listOfLists.add(new ArrayList<String>());
}
And you will use it like this :
listOfLists.get(0).add("foobar");
But if you really want to "create a 2D array that each cell is an ArrayList!"
Then you must go the dijkstra way.
listOfLists structure this way! You are iterating through an empty structure so the for will do nothing and the following get will then throw an exception.
ArrayList<String>[][] list = new ArrayList[10][10];
list[0][0] = new ArrayList<>();
list[0][0].add("test");
This can be achieve by creating object of List data structure, as follows
List list = new ArrayList();
For more information refer this link
