Wants to get selected index fron a JList. But returns -1

Wants to get selected index fron a JList. But returns -1

I made a jlist and set a default list model using setModel method. When I
called getSelectedIndex(), it returns -1. Why is it?
if (!listAdded.isSelectionEmpty()) {
listModelAdded.removeElementAt(listAdded.getSelectedIndex());
listBankQuestions.remove(listAdded.getSelectedIndex());
System.out.println(i);
--i;
System.out.println("Selected : " + listAdded.getSelectedIndex());
}