You mean display only one element of the array?
You can create an array that has only one element, the element you want to display. But that would make the JList useless since that is not its purpose. Maybe you can change the way you add the JList to the frame, make it a bit wider.
Also if you look at the API there is an example on how to add scrolling to the list.
If you had already thought of that, sorry but that was my thought too.
Another thing would be to make a custom ListModel. Again check the API of the JList