[1899] in java-interest
Re: Q: array initialization.
daemon@ATHENA.MIT.EDU (Arthur van Hoff)
Tue Sep 19 18:12:57 1995
Date: Tue, 19 Sep 1995 11:40:16 -0800 (PDT)
From: Arthur van Hoff <Arthur.Vanhoff@Eng.Sun.COM>
Reply-To: Arthur van Hoff <Arthur.Vanhoff@Eng.Sun.COM>
To: Christophe Meessen <meessen@cppm.in2p3.fr>
Cc: java-interest@java.Eng.Sun.COM
Hi Christphe,
> I wrote the following command
>
> SortElem v[] = new SortElem[10];
>
> What is this command supposed to do ?
It creates an array of length 10. Each element will be initialized to null.
> Are SortElem instances created ?
No.
> If yes
> what constructor is called ?
> how many instances are created ?
It doesn't work that way.
> According to the reference manual (page 6) this is the way an array of
> instances is created.
Yes.
>
> Here is a small program that didn't do what I expected
>
> Suppose a class SortElem;
>
> public class SortElem[
> public int val;
> ...
> }
>
>
> later...
>
> static SortElem v[] = new SortElem[3];
>
> v[0].val = 2;
> v[1].val = 5;
> v[2].val = 8;
>
> for( int i = 0; i < v.length; i++ )
> System.out.println( v[i].val );
>
> very simple.
>
> And the result is....
>
> 8
> 8
> 8
>
> Not exactly what I would have expected.
> It is as if only one instance is created and all array elements hold a
> reference to that object !
Only the array is created. You will need to create and assign a SortElem
to each position in the array for it to work.
> This is not the same as in C++ where as many instance are created as there
> are elements in the array and for each one of them the default constructor
> (with no argument) is called.
Right, it is not the same as C++. The array contains references to SortElems,
it doesn't contain the SortElems themselves.
> Bien cordialement,
Goedenmiddag.
Have fun,
Arthur van Hoff
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