具有固定/可变arity（varargs）匹配的最具体方法

Question

In section 15.12.2.5 of the Java Language Specification , it talks about how to choose the most specific method in both cases of methods with fixed arity and methods of variable arity (ie varargs ).

What I can't find in the JLS is anything about deciding between two methods where one is of fixed arity and one of variable arity however. For example:

public interface SomeApi {
    public String getSomething(String arg);       // method 1
    public String getSomething(String ... args);  // method 2
}

Compiles just fine as one would expect ( for reasons outlined by Yoni below ). This calling code compiles also:

SomeApi api = ...
Object o = api.getSomething("Hello");

and if you run it, method #1 (ie the non-varargs method) is called. Why is this calling-code not ambiguous? Why is the fixed arity method more specific than the variable-arity one? Can someone point me to the relevant bit of the spec?

Answer 1

The first method resolution phase considers only fixed arity methods and the process is terminated if a match is found, before any varargs methods are considered.

From http://docs.oracle.com/javase/specs/jls/se6/html/expressions.html#15.12.2.2

15.12.2.2 Phase 1: Identify Matching Arity Methods Applicable by Subtyping

If no method applicable by subtyping is found, the search for applicable methods continues with phase 2 (§15.12.2.3). Otherwise, the most specific method (§15.12.2.5) is chosen among the methods that are applicable by subtyping.

(My emphasis.)

Answer 2

I can't point you to the spec, but logically,

getSomething(String...args) 

translates to

getSomething(String[] args)

with no ambiguity