How does this output comes?

[Sumit Patil]

Hi,

Please study the code below.

public class Confusing
{
	public Confusing(Object o)
	{
		System.out.println("Object");
	}
	public Confusing(Object[] d)
	{
		System.out.println("Object[] array");
	}
	
	public static void main(String[] arg)
	{
		new Confusing(null);
	}

}

The Output is "Object[] array", i am not able to get this behavior.

Can you please help?

Thanks.

[stanislav bashkirtsev]

You should pass array of objects! F.i.

new Confusing(arg);

[Sumit Patil]

stanislav bashkirtsev wrote:You should pass array of objects! F.i.

Actually i want to know how the output comes as shown when i pass a 'null'

[Jesper de Jong]

Please use a meaningful subject line instead of something like "Quite Confusing".

[Vijitha Kumara]

Sumit Patil wrote:Actually i want to know how the output comes as shown when i pass a 'null'

Because any object reference can be "null". So you are allowed to pass null where a reference of any object is expected.
Compiler matches the most specific one hence the Object[] type argument and not the Object type argument. Is this answer your question?

[Sumit Patil]

Because any object reference can be "null". So you are allowed to pass null where a reference of Object (in this case) is expected

The same holds true for first constructor.
Why does the second constructor gets called and not the first one?

[Vijitha Kumara]

Sumit Patil wrote:The same holds true for first constructor.Why does the second constructor gets called and not the first one?

You have asked just when I was editing my reply above which I added the reason why

[Sumit Patil]

You have asked just when I was editing my reply above which I added the reason why

Sorry....

Ok....is this the only reason? why can't it call the first constructor?

[Vijitha Kumara]

Otherwise it would be ambiguous to the compiler because both can accept null.

[Nitish Bangera]

Actually when you pass null to a overloaded method or a overloaded Constructor, the most subtype in the inheritance hierarchy parameter method is chosen and run. As you can see Object[] extends from Object, that is the most subtype in the current scenario(can add a constructor having String[] parameter which will will run). But this is valid only if the parameters fall in the same hierarchy. If some other parameter comes then it will be an error(if String[] is changed to String).

[Sumit Patil]

Thanks ....

Got it...