Generics in Java array

Question

To start with there are multiple posts on SO itself which explain why Generics and arrays do not mix in Java.

But my question is - if that is so why do I get a warning in Eclipse when I do something like the following and how to get rid of this warning message.

private RotatingQueue<RotatingQueueData> rQueue[] =  new RotatingQueue[15];

Warning: Multiple markers at this line - Type safety: The expression of type RotatingQueue[] needs unchecked conversion to conform to RotatingQueue[]

What happens if you change the right hand side of the assignment to new RotatingQueue<RotatingQueueData>[15] ? — Dawood ibn Kareem
– Dawood ibn Kareem, Commented Mar 31, 2014 at 8:17
Even better: new RotatingQueue<>[15]? (Java 7 is out, even Java 8) — user1907906
– user1907906, Commented Mar 31, 2014 at 8:18
Yes, I know, but I didn't want to introduce a new unknown, given that we don't know what version Andy is running. — Dawood ibn Kareem
– Dawood ibn Kareem, Commented Mar 31, 2014 at 8:22
@DavidWallace & LutzHorn Neither of those would work. Creation of array of parameterized type is not allowed. — Rohit Jain
– Rohit Jain, Commented Mar 31, 2014 at 8:22
@Andy897 Yup. You can suppress it though. Even better would be avoid create array of parameterized types. Rather use List<RotatingQueue<RotatingQueueData>>. — Rohit Jain
– Rohit Jain, Commented Mar 31, 2014 at 8:30

Harmlezz · Accepted Answer · 2014-03-31 08:23:58Z

3

It is not possible to create an array of a parameterized type. Hence you have to live with the warning, but may ignore it like this:

@SuppressWarnings("unchecked")
List<String> lists[] = new List[15];

I don't know about any other way to do this if you try to continue to work with List<String>.

answered Mar 31, 2014 at 8:23

Harmlezz

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