I wrote a piece of code like this
ArrayList<Integer>[]list=new ArrayList<Integer>[128];
But Eclipse says
Cannot create a generic array of ArrayList
I also tried code like this
ArrayList<Integer>[]list=(ArrayList<Integer>[])new Object[128];
But Eclipse throws exception:
[Ljava.lang.Object; cannot be cast to [Ljava.util.ArrayList;
So how can I build an array of ArrayList< Integer > ?
Thanks a lot!!
List<Integer> inp = new ArrayList<Integer>(10) to create list of integers whose size is 10.
From what I see you are trying to create an ArrayList and an Array in the same step, which is impossible.
An Arraylist differs from arrays as it is a generic class, which means it has a lot more functionality.
For example:
In your code you are trying to specify a limit to the ArrayList, ArrayLists don't have a limit, they are expandable.
You can use the .add() function to add objects to ArrayLists, and get values using the .get(int index) function.
Example code:
ArrayList<Integer> myArray = new ArrayList<Integer>(); //initialized a new arrayList
myArray.add(7); //added element 7 at index 0
myArray.add(12); // added element 12 at index 1
print(myArray.get(1)) //output 12
You can check the documentations for the ArrayList class here.
Hope that helped.
Your question isn't really clear, but to build an array list,this code should be sufficient
ArrayList<Integer> list;
list = new ArrayList<Integer>(128);
Use this to create an ArrayList (remember, ArrayLists always have a theoretically indefinite capacity, since you can always add more elements to them - see a tutorial):
ArrayList<Integer> list = new ArrayList<>();
or this to make an array of ArrayLists:
ArrayList<Integer>[] lists = new ArrayList[128];
You will of course have to initialize your ArrayLists:
for (int i = 0; i < lists.length; i++)
lists[i] = new ArrayList<>();
Alternatively, you can create an ArrayList of ArrayLists:
ArrayList<ArrayList<Integer>> lists2 = new ArrayList<>();
for (int i = 0; i < 128; i++)
lists2.add(new ArrayList<>());
