Datastructures problem

I think you're looking for an ArrayList ( http://java.sun.com/j2se/1.4.2/docs/api/java/util/ArrayList.html).

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ArrayList has a method get( int index ). you can do:

ArrayList myArrayList = new ArrayList();

// put stuff in myArrayList

for ( int i = 0; i < myArrayList.size(); i++ ) {
System.out.println ( myArrayList.get( i ));
}

Note: the get method returns an Object, so in some cases you may find that you need to cast it (if you are casting to an int, float, etc. you need to use the classes Integer, Float, etc.)

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What do you mean when you use the phrase that you don't "know how to refer to an object in an arraylist"?

If you need to have some "key" which allows you to put an "external identity" a particular object being stored in the arraylist, you need to use a Map (key, value) implementation - you look for the key and then extract the value associated with the key of interest. If you just want to iterate through the elements being stored in the arraylist, use an Iterator (or ListIterator). If you want to do something to each and every element in the list, use the extended for-each control (introduced in Java 1.5).

Also with Java 1.5, you can use generic identification to have the compiler check that all of the elements being stored in the ArrayList<datatype> is of a certain datatype - in that way, you aren't forced to use casting to establish the datatype of the Object being retrieved from the ArrayList.