j.ul.Objects follow-up: methods for var-argification? (original) (raw)

Joseph D. Darcy Joe.Darcy at Sun.COM
Fri Oct 9 18:46:35 UTC 2009

Ulf Zibis wrote:

Am 08.10.2009 20:34, Joseph D. Darcy schrieb:

Hello.

In the discussion about java.util.Objects, a few existing JDK methods were mentioned for possible var-argification: java.util.Arrays.hashCode(Object[] a) java.util.Arrays.deepHashCode(Object[] a) java.util.Arrays.toString(Object[] a) Also of possible general interest are some methods on String (bug 6762452 API change proposal: Enhance String constructor for varargs) java.lang.String.copyValueOf(char[] data) java.lang.String.valueOf(char[] data) java.lang.String(char[] value) Var-argification is fully binary compatible and is generally source compatible, although new conversions are allowed of course and overloadings may change. As String is final, there are no changed overloadings. As the Arrays methods are static, there are too no changed overloadings.

Being final and static alone are not enough to guarantee no new overloadings; although the overloading resolution rules are carefully crafted to try to select the same method if var-args is added to a class.

OK, correct me, if I'm wrong.

FYI, here is a var-argification which breaks source compatibility:

Consider in final class C

Before: static void foo(int..) static void foo(Integer[])

After: static void foo(int...) static void foo(Integer...)

Call site:

C.foo(42);

In the after scenario, both versions of foo could now be called and there is an ambiguity whereas before only the int... method could have been called.

For some interesting discussion of overloading, see http://gbracha.blogspot.com/2009/09/systemic-overload.html

-Joe

More information about the core-libs-dev mailing list