Explanation ....

[Vasiq Molvizadah]

I'm reading this Kathy Sierra Book and in one program...the output is kinda confusing...

  class A
    {

    }

    class B extends A
    {

    }

    class ComingThru
    {
        static String s = "-";
        public static void main(String[] args)
        {
            A[] aa = new A[2];
            B[] bb = new B[2];
            sifter(aa);
            sifter(bb);
            sifter(7);
            System.out.println(s);
        }
        static void sifter(A[]... a2)
        {
            System.out.println("I'm in sifter A[]...");
            s += "1";
        }
        static void sifter(B[]... b2)
        {
            System.out.println("I'm in sifter B[]...");
            s += "2";
        }
        static void sifter(B[] b1)
        {
            System.out.println("I'm in B[]");
            s += "3";
        }
        static void sifter(Object o)
        {
            System.out.println("In object method");
            s += "4";
        }
    }  

The output of the program is
-434

I'm not getting this....any help

[Rob Spoor]

A[] matches both A[]... and Object. Varargs is only used if no other method matches. That is why sifter(aa) uses Object and not A[]... It's also why B[] is used and not B[]...
Finally, 7 matches nothing directly. It is therefore boxed to Integer which then matches Object.

[Campbell Ritchie]

Which Kathy Sierra book? You should always quote your sources. And "Explanation ...." doesn't tell us much of what the thread is about.

[Vasiq Molvizadah]

Campbell Ritchie wrote:Which Kathy Sierra book? You should always quote your sources. And "Explanation ...." doesn't tell us much of what the thread is about.

The name of the book is SCJP for Java 6 Study Guide - by Kathy Sierra and Bert Bates and I apologize for not giving a proper thread name.....

[Vasiq Molvizadah]

Rob Prime wrote:A[] matches both A[]... and Object. Varargs is only used if no other method matches. That is why sifter(aa) uses Object and not A[]... It's also why B[] is used and not B[]...
Finally, 7 matches nothing directly. It is therefore boxed to Integer which then matches Object.

Thanks for the explanation Rob.....

[Campbell Ritchie]

Thank you for the information, and apology accepted.