What does a tilde in angle brackets mean when creating a Java generic class?

Question

I was reading through some JMockit examples and found this code:

final List<OrderItem> actualItems = new ArrayList<~>();

What does the tilde in the generic identifier mean? I know it's the unary bitwise NOT operator, but I don't see an operand here.

Also, I tried compiling it and got an error. Am I just missing something?

score 175 · Accepted Answer · edited Apr 08 '18 at 06:16

175

It is just a shorthand for "same as in declaration".

Some IDEs, e.g. IntelliJ use this too.

The files on disk do not have this notation, which is only a compaction in the IDE GUI.

edited Apr 08 '18 at 06:16

roottraveller

answered Feb 03 '11 at 15:12

openCage

1

It was an Intellij screenshot. – Michael K Feb 03 '11 at 15:30
1

Just for personal clarification - IntelliJ produces Java source files with *this* notation, iaw, source files with illegal Java content??? Or is this just the *view* of the source and the saved file is correct? – Andreas Dolk Feb 03 '11 at 15:53
5

@Andreas_D: It is just a view. The files on disk are ok. – openCage Feb 03 '11 at 15:54
8

And actually, the tilde is grayed (to indicate that it's different), and if you click on it, it'll expand to the full definition. – yshavit Sep 13 '13 at 17:58
1

This can be disabled in the intelij settings for editor/general/Code Folding. – Ocie Mitchell Jun 05 '18 at 01:05

score 20 · Answer 2 · answered Feb 03 '11 at 15:51

20

If there wasn't a tilde, I'd say, the code was already Java 7. Java 7 allows the diamond operator so this is/will be legal Java code:

Map<String, List<String>> map = new HashMap<>();

(but - no tilde with this syntax)

answered Feb 03 '11 at 15:51

Andreas Dolk

score 14 · Answer 3 · answered Feb 19 '15 at 22:50

14

In IntelliJ IDEA, the ~ here:

Set<String> associations = new LinkedHashSet<~>();

means String, which is the same as in the declaration on the left side.

answered Feb 19 '15 at 22:50

Ascendant

score 2 · Answer 4 · answered Feb 03 '11 at 15:12

2

I think that is shorthand to mean whatever the type is, in this case OrderItem.

answered Feb 03 '11 at 15:12

Andrew White

4 Answers4