In Scala, what is the difference between Any and Object?

Question

Suppose I have the following java method

protected void onEvent(Object obj) {

    }

The Scala compiler accepts

protected override def onEvent(event: Any)

and

protected override def onEvent(event: Object)

Is there any difference between the two?

score 26 · Answer 1 · answered Aug 23 '11 at 12:26

26

Any includes things that are not Objects in Java; it includes primitive types and also Nothing. Object is the same class as in Java, so it definitely excludes primitives.

answered Aug 23 '11 at 12:26

Ernest Friedman-Hill

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So if you are attempting to a Java method that uses Object, does Any get you into trouble if you pass in a primitive or is it implicitly converted? – James McMahon Jul 15 '12 at 14:19
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@James i tried `def met(a: java.lang.Object) = {}; val i = 10; met(i)` and here's the output from compiler: *error: the result type of an implicit conversion must be more specific than AnyRef* http://stackoverflow.com/a/26550576/4541480, it worked with `val i: java.lang.Integer = 10` (not with default `val i: Int = 10` – Nicofisi Mar 18 '17 at 13:50

score 26 · Accepted Answer · answered Aug 23 '11 at 12:41

26

There is an article on scala-lang with great diagram (I even put it on the wall). And also need to be mentioned:

If Scala is used in the context of a Java runtime environment, then scala.AnyRef corresponds to java.lang.Object.

answered Aug 23 '11 at 12:41

4e6

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Correct. Note that `AnyRef` is not `Any`, but a subclass. `Any` has subclass `AnyVal` also. – Ernest Friedman-Hill Aug 23 '11 at 12:43
@Ernest Yes. The chart shows it very clear. Don't understand. Is there something I missed? – 4e6 Aug 23 '11 at 12:50
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no, you didn't miss anything; I just wanted to clarify for people who didn't follow the link. – Ernest Friedman-Hill Aug 23 '11 at 12:51

In Scala, what is the difference between Any and Object?

2 Answers2