Generic array creation error

Question

I am trying do something like this:-

public static ArrayList<myObject>[] a = new ArrayList<myObject>[2]; 

myObject is a class. I am getting this error:- Generic array creation (arrow is pointing to new.)

Answer 1

You can't have arrays of generic classes. Java simply doesn't support it.

You should consider using a collection instead of an array. For instance,

public static ArrayList<List<MyObject>> a = new ArrayList<List<MyObject>(); 

Another "workaround" is to create an auxilliary class like this

class MyObjectArrayList extends ArrayList<MyObject> { } 

and then create an array of MyObjectArrayList.

---

Here is a good article on why this is not allowed in the language. The article gives the following example of what could happen if it was allowed:

List<String>[] lsa = new List<String>[10]; // illegal Object[] oa = lsa;  // OK because List<String> is a subtype of Object List<Integer> li = new ArrayList<Integer>(); li.add(new Integer(3)); oa[0] = li;  String s = lsa[0].get(0);  

Answer 2

There is a easier way to create generic arrays than using List.

First, let

public static ArrayList<myObject>[] a = new ArrayList[2]; 

Then initialize

for(int i = 0; i < a.length; i++) {      a[i] = new ArrayList<myObject>(); }