ADDITIONAL SYSTEM INFORMATION :
openjdk 19.0.2 2023-01-17
OpenJDK Runtime Environment (build 19.0.2+7-Ubuntu-0ubuntu322.04)
OpenJDK 64-Bit Server VM (build 19.0.2+7-Ubuntu-0ubuntu322.04, mixed mode, sharing)

OS: Ubuntu 22.04.2 LTS x86_64
Kernel: 5.19.0-46-generic



A DESCRIPTION OF THE PROBLEM :
ListSelectionEvent#getFirstIndex() and ListSelectionEvent#getLastIndex() return incorrect values if the event is fired from a JList that has its selection mode set to SINGLE_SELECTION.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Using the provided source code:

1. Launch the program
2. Select an element
3. Select a different element

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The assertion on line 58 should pass.

The first index and the last index should be the same value.
ACTUAL -
The assertion on line 58 does not pass.

One of the indexes is always the same as the previous selection. This makes it impossible to determine which element was actually selected.

---------- BEGIN SOURCE ----------
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridLayout;

import javax.swing.DefaultListModel;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.ListSelectionModel;
import javax.swing.border.EmptyBorder;
import javax.swing.JList;

public class Test extends JFrame {

private JPanel contentPane;
private JList<String> list = new JList<>();
private DefaultListModel<String> stringList = new DefaultListModel<>();

/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Test frame = new Test();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}

/**
* Create the frame.
*/
public Test() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));

setContentPane(contentPane);

for(int i = 0; i < 10; i++) {
StringBuilder b = new StringBuilder();
for(int j = 0; j < 15; j++) {
b.append(i);
}
stringList.addElement(b.toString());
}

JPanel panel = new JPanel();

list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); //can only select one element at a time
list.setModel(stringList);
list.addListSelectionListener((e) -> {
if(e.getFirstIndex() != e.getLastIndex()) {
System.err.println(e);
throw new AssertionError(e.getFirstIndex() + " != " + e.getLastIndex()); //since only one element can be selected, the first index and the last index should be the same
}
});
panel.add(list);

this.setLayout(new GridLayout(1,1));
contentPane.add(panel, BorderLayout.CENTER);
}

}
---------- END SOURCE ----------

FREQUENCY : always