Select the first item : JList Selection « Swing « Java Tutorial

import javax.swing.JList;

public class Main {
  public static void main(String[] argv) throws Exception {
    String[] items = { "A", "B", "C", "D" };
    JList list = new JList(items);

    int start = 0;
    int end = 0;
    list.setSelectionInterval(start, end);

14.43.JList Selection
14.43.1.List selection event
14.43.2.A single-selection JList.
14.43.3.Listening for Changes to the Items in a JList Component
14.43.4.Listening for Changes to the Selection in a JList Component
14.43.5.Setting the Selection Mode of a JList Component
14.43.6.The selected items must be in a contiguous range
14.43.7.Multiple ranges of selected items are allowed
14.43.8.Setting the Selected Items in a JList Component
14.43.9.Select all the items
14.43.10.Clear all selections
14.43.11.Select the first item
14.43.12.Add another selection - the third item
14.43.13.Deselect the first item
14.43.14.Getting the Selected Items in a JList Component
14.43.15.Get the index of the last selected item
14.43.16.Determine if there are any selected items