java diamond operator doesn't compile

Question

When I try to use the diamond operator as follows:

List<DateTimeZone> list = new ArrayList<>();

It works perfectly.

However, when I try this:

List<DateTimeZone> list = false ? null : new ArrayList<>();

It doesn't compile, messaging: "Incompatible types: required List, found ArrayList".

Why is that?

May be you have custom `List` or `ArrayList` class (not from `java.util` package) — Ilya, Sep 18 '14 at 12:45

score 4 · Accepted Answer · edited May 23 '17 at 11:52

4

The ternary operator and the diamond operator don't get along very well. You have to specify the type explicitly:

List<Date> list = false ? null : new ArrayList<Date>();

More info at these related questions:

edited May 23 '17 at 11:52

Community

answered Sep 18 '14 at 12:46

Kevin Workman

+1, So can we conclude that, conditional operator doesn't work with diamond operator ? – Suresh Atta Sep 18 '14 at 12:47
@sᴜʀᴇsʜᴀᴛᴛᴀ It works, but not in Java 7. – Marko Topolnik Sep 18 '14 at 12:48
generics inference is best used with Java8 – Kumar Abhinav Sep 18 '14 at 13:53

1 Answers1