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Index › Programming Questions & Help › Syntax Questions › Array instantiation..

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Array instantiation.. (Read 1042 times)

vade

Array instantiation..
Jun 2^nd, 2005, 5:00am

Hi. Heres a question. Why does one have to pass the length / count of an array when creating it?

Id like to be able to add items to an array an not know how many elements I will have when im creating it. However, all of the examples Ive seen in the tutorials/reference always give a 'maxnumber' or 'arraymax' of some sort and pass that as the length when creating.

Why cant I do a

String[] urlArray = new String[];

And then just add them to the end of the array?

urlArray[i] = "http://example.com";
urlArray[i+1] = http://example2.com"; //etc.

The reason Im asking is because im integrating a mysql backend to some data visualization I am doing. I dont know ahead of time how many rows are being returned, and the only workaround I can see is doing 'expensive' 'count(row) as arraytotal' sql queries when I shouldnt have to?

Am I simply overlooking something? Is this a java thing? Im a PHP guy, and Im used to not having to worry about this. Sorry, im a proce55ing newb, so just point me in the right direction.

Thanks.

//./;[]/// http://abstrakt.vade.info

mflux

Re: Array instantiation..
Reply #1 - Jun 2^nd, 2005, 7:38am

what you're looking for is this beautiful little gem named append()

http://processing.org/reference/append_.html

However append only supports int, float, char, string, and normal stuff. If you want to append your own objects to your own object arrays, then you need to extend/overload append yourself. To do this, use System.arraycopy(). You can google that function and find out the rest :]

Portfolio

mark hill

Re: Array instantiation..
Reply #2 - Jun 2^nd, 2005, 8:57am

If you find append() doesn't do everything you'd like try the Vector class.

Code:



Vector list;

list = new Vector();

The size of a vector is variable, though you might also checkout arrayList which has less functionality, but is quicker for it. It can contain references to Objects etc. Very flexible

Here's the documentation for it.

http://java.sun.com/j2se/1.4.2/docs/api/java/util/Vector.html

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