JList needs ability to set multiple selection via input device

cynthia.castillo@Eng 1997-12-19

I am able to progrmmatically set the multiple selected indices via JList setSelectedIndices() method, but could not use the input device (keyboard
and/or mouse) to add to the already selected items. When trying to select
an item not yet selected, all previously selected items that were set programmatically are all deselected and only one item shows as selected. I tried to select a second item with Shift + left mouse click to select another, but previously selected item is deselected.

Please provide similar behaviors as awt.List: clicking an already selected item, deselects it and clicking on an item not yet selected, selects it and when
the multipleMode is set, a newly selected item is added to the existing set of selected items.