Diamond Generic and Legacy in Java

Question

In Collections I've found the following:

@SuppressWarnings("unchecked")
public static final List EMPTY_LIST = new EmptyList<>();

I really can't find any reason to use:

new EmptyList<>()

here instead of:

new EmptyList()

as it would be for java < 1.7.

Is there any difference between this approach?

@ByteCode You'll find it at line 3185, in `Collections`'s source. — afsantos, Nov 06 '13 at 15:47
No, no difference in that case, except that you'll get a warning when you don't specify the generic type parameter when instantiating a generic type. — isnot2bad, Nov 06 '13 at 15:48
See http://stackoverflow.com/questions/2770321/what-is-a-raw-type-and-why-shouldnt-we-use-it — isnot2bad, Nov 06 '13 at 15:49
It makes no difference - as a side note, you should use `Collections.emptyList()` instead to avoid the unchecked conversion warning. — assylias, Nov 06 '13 at 15:56

score 2 · Answer 1 · edited May 23 '17 at 12:08

2

If you are concerned only about <> operator then you should see What is the point of the diamond operator in Java 7?.

Regarding EMPTY_LIST: Either you do :

@SuppressWarnings("rawtypes")
List list = Collections.EMPTY_LIST;

OR Something like:

List<String> s = Collections.emptyList();

The reason to use <> operator is maintaining compile time checking for raw types. The above links describes that well.

edited May 23 '17 at 12:08

Community

answered Dec 05 '13 at 15:24

Raju Singh

1

I think he knows what's the point of diamond operator. He is just asking what's the point behind it in the scenario he has shown. – Adam Dyga Dec 05 '13 at 15:38

1 Answers1