How is the component type for the varargs array determined?

Question

When you use varargs, how is the component type of the resulting array determined?

For example, is this program guaranteed to print true or is its behaviour technically unspecified?

public static void main(String[] args) {
    foo("", 0);
}

static <T> void foo(T... arr) {
    System.out.println(arr.getClass() == Serializable[].class);
} 

Answer 1

I ran this code and the output tells you have no guarantees (at least if classes have more than one common ancestor on different hierarchy branches)

Honestly I don't know the reasons behind this magic, but I just could not post it as a comment

import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone
{

  interface A{}
  interface B{}
  class AB implements A, B {}
  class BA implements A, B {}

    public static void main (String[] args) throws java.lang.Exception
    {
        foo(new AB(), new BA());
        foo2(new AB(), new BA());
    }

    static <T> void foo(T... arr) {
        System.out.println(arr.getClass() == A[].class);
    }

    static <T> void foo2(T... arr) {
        System.out.println(arr.getClass() == B[].class);
    } 
}

output

true
false

More weird things:

If interface B is declared before interface A, result is the opposite:

false
true

Changing order of arguments in method call, method declaration order and order of interfaces in implements block does not make effect for me (1.8.0_51).