<p>While creating classes in Java I often find myself creating instance-level collections that I know ahead of time will be very small - less than 10 items in the collection. But I don't know the number of items ahead of time so I typically opt for a dynamic collection (ArrayList, Vector, etc).</p>

<pre><code>class Foo
{
  ArrayList&lt;Bar&gt; bars = new ArrayList&lt;Bar&gt;(10);
}
</code></pre>

<p>A part of me keeps nagging at me that it's wasteful to use complex dynamic collections for something this small in size. Is there a better way of implementing something like this? Or is this the norm?</p>

<p>Note, I'm not hit with any (noticeable) performance penalties or anything like that. This is just me wondering if there isn't a better way to do things.</p>

The overhead is very small. It is possible to write a hybrid array list that has fields for the first few items, and then falls back to using an array for longer list.
You can avoid the overhead of the list object entirely by using an array. To go even further hardcore, you can declare the field as Object, and avoid the array altogether for a single item.
If memory really is a problem, you might want to forget about using object instances at the low-level. Instead use a larger data structure at a larger level of granularity.