Question

Does anyone know how to fix this warning?

MyMain.java:12: warning: [unchecked] unchecked conversion
found   : java.util.ArrayList[][]
required: java.util.ArrayList<java.lang.String>[][]
            obj[count].someArrayList = new ArrayList[4][4];

I tried to change this to:

obj[count].someArrayList = new ArrayList<String>[4][4];

But the amendment changes the warning into the following error:

MyMain.java:12: generic array creation
            obj[count].someArrayList = new ArrayList<String>[4][4];

The declaration of someArrayList is:

public ArrayList<String>[][] someArrayList;

Answer 1

You cannot create arrays with generics (hence the error). The warning indicates the heavily discouraged use of raw types with an ArrayList.

Instead, the following creates a multidimensional ArrayList:

public ArrayList<ArrayList<String>> someArrayList;

You can then perform normal operations on your multidimensional ArrayList.

obj[count].someArrayList = new ArrayList<ArrayList<String>>();
ArrayList<String> toAdd = new ArrayList<String>();
toAdd.add("test");
toAdd.add("test2");
obj[count].someArrayList.add(toAdd);