Using arrays of objects ?

[TonyB]

I'm new to java, and would like some advice on how to keep track of groups
of objects where the number of objects is not predefined.
For example say I have a toolbox class which contains an arbitrary number of
tool objects. I want to have a method to add a tool to the toolbox object,
and other methods to list the current contents of the toolbox for example.
I could keep a reference to each tool object as added in an array of type
tool but an array is declared with a fixed length, so short of defining the
array to have a some arbitrary large size I can't see how to deal with this
list of objects. I don't want to use a database at this time.
Is there a better way to do this ?
Tony

[Casey Hawthorne]

Re: Using arrays of objects ?

Read up on collection classes and post to comp.lang.java. help
--
Regards,
Casey

[Mark Rafn]

Re: Using arrays of objects ?

TonyB <tonyb@kerriswa y.freeserve.co. ukwrote:

>I'm new to java, and would like some advice on how to keep track of groups
>of objects where the number of objects is not predefined.

java.util.Colle ction and friends make this pretty easy.

>I could keep a reference to each tool object as added in an array of type
>tool but an array is declared with a fixed length, so short of defining the
>array to have a some arbitrary large size I can't see how to deal with this
>list of objects. I don't want to use a database at this time.

ArrayList<Tooli s the most common way to do this. Depending on your needs,
you may prefer a HashSet, TreeSet, LinkedList, or some other Collection that
fits your performance and usage requirements.
--
Mark Rafn dagon@dagon.net <http://www.dagon.net/>

[Joanna]

Re: Using arrays of objects ?


"TonyB" <tonyb@kerriswa y.freeserve.co. ukwrote in message
news:E9JDh.8799 6$tQ1.64679@fe0 4.news.easynews .com...

I'm new to java, and would like some advice on how to keep track of groups
of objects where the number of objects is not predefined.
For example say I have a toolbox class which contains an arbitrary number

of

tool objects. I want to have a method to add a tool to the toolbox object,
and other methods to list the current contents of the toolbox for example.
I could keep a reference to each tool object as added in an array of type
tool but an array is declared with a fixed length, so short of defining

the

array to have a some arbitrary large size I can't see how to deal with

this

list of objects. I don't want to use a database at this time.
Is there a better way to do this ?
Tony

here we go

http://cs.gettysburg.edu/~cpresser/java/ForLoopTest.html

Joanna

[j1mb0jay]

Re: Using arrays of objects ?

TonyB wrote:

I'm new to java, and would like some advice on how to keep track of
groups of objects where the number of objects is not predefined.
For example say I have a toolbox class which contains an arbitrary
number of tool objects. I want to have a method to add a tool to the
toolbox object, and other methods to list the current contents of the
toolbox for example. I could keep a reference to each tool object as
added in an array of type tool but an array is declared with a fixed
length, so short of defining the array to have a some arbitrary large
size I can't see how to deal with this list of objects. I don't want
to use a database at this time. Is there a better way to do this ?
Tony

ArrayLists would seem to the answer for what you are looking for.

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

There is a Iterator class for going through each of the objects in a array,
try not to store objects in an array, try to type them first (looking into
Interfaces).

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

http://java.sun.com/docs/books/tutorial/java/concepts/interface.html

--
Regards JJ (UWA)

[TideRider]

Re: Using arrays of objects ?

I would probably use an ArrayList (from java.util). I would also define either an
interface or base class for Tool, from which all of the tools are derived, and
(using Java 5 or higher) parameterize the ArrayList:

ArrayList<Toolt oolbox = new ArrayList<Tool> ();

To operate on Tool in the toolbox (again, with Java 5 or higher), you can use:

for (Tool tool : toolbox)
{
//tool variable contains the current tool
}


--
TideRider


"TonyB" <tonyb@kerriswa y.freeserve.co. ukwrote in message news:E9JDh.8799 6$tQ1.64679@fe0 4.news.easynews .com...
| I'm new to java, and would like some advice on how to keep track of groups
| of objects where the number of objects is not predefined.
| For example say I have a toolbox class which contains an arbitrary number of
| tool objects. I want to have a method to add a tool to the toolbox object,
| and other methods to list the current contents of the toolbox for example.
| I could keep a reference to each tool object as added in an array of type
| tool but an array is declared with a fixed length, so short of defining the
| array to have a some arbitrary large size I can't see how to deal with this
| list of objects. I don't want to use a database at this time.
| Is there a better way to do this ?
| Tony
|
|

[Lew]

Re: Using arrays of objects ?

TideRider wrote:

I would probably use ...

Just so you know, many newsreaders, mine included, clip material that follows
your sig in the reply, and display it "dimmed" or gray in the initial reading.
This happened with your replies, which were top-posted.

Top-posting also disrupts the flow of the message and makes it harder to read.

Please don't top-post.

As to your suggestion to use

ArrayList<Toolt oolbox = new ArrayList<Tool> ();

It'd likely be better to use

List<Tooltoolbo x = ...

or even

Collection<Tool toolbox = ...

For example, if a given Tool should appear only once in 'toolbox', then the
implementing class might better be a Set<Tool>.

--
Lew