Add IntegerProperty selectedIndexProperty(JList<?> list).

src/main/java/io/github/parubok/fxprop/ListSelectedIndexPropertyImpl.java

@@ -0,0 +1,45 @@
+package io.github.parubok.fxprop;
+
+import io.github.parubok.swingfx.beans.property.IntegerProperty;
+import io.github.parubok.swingfx.beans.property.SimpleIntegerProperty;
+import io.github.parubok.swingfx.beans.value.ChangeListener;
+
+import javax.swing.JList;
+import javax.swing.event.ListSelectionListener;
+import java.util.Objects;
+
+import static io.github.parubok.fxprop.ClientProps.PROP_SELECTED_INDEX;
+
+/**
+ * Selected index of {@link JList}.
+ */
+final class ListSelectedIndexPropertyImpl {
+    private static final ListSelectionListener SELECTION_LISTENER = e -> {
+        JList<?> list = (JList) e.getSource();
+        int selectedIndex = list.getSelectedIndex();
+        IntegerProperty p = (IntegerProperty) list.getClientProperty(PROP_SELECTED_INDEX);
+        if (p.get() != selectedIndex) {
+            p.set(selectedIndex);
+        }
+    };
+
+    private static final ChangeListener<Number> FX_PROP_LISTENER = (observable, oldValue, newValue) -> {
+        IntegerProperty p = (IntegerProperty) observable;
+        JList<?> list = (JList) p.getBean();
+        if (newValue.intValue() != list.getSelectedIndex()) {
+            list.setSelectedIndex(newValue.intValue());
+        }
+    };
+
+    static IntegerProperty getProperty(JList<?> list) {
+        Objects.requireNonNull(list, "list");
+        SimpleIntegerProperty p = (SimpleIntegerProperty) list.getClientProperty(PROP_SELECTED_INDEX);
+        if (p == null) {
+            p = new SimpleIntegerProperty(list, "selectedIndex", list.getSelectedIndex());
+            list.putClientProperty(PROP_SELECTED_INDEX, p);
+            list.addListSelectionListener(SELECTION_LISTENER);
+            p.addListener(FX_PROP_LISTENER);
+        }
+        return p;
+    }
+}

src/main/java/io/github/parubok/fxprop/SelectedValuePropertyImpl.java → src/main/java/io/github/parubok/fxprop/ListSelectedValuePropertyImpl.java

@@ -13,7 +13,7 @@
 /**
  * Selected value of {@link JList}.
  */
-final class SelectedValuePropertyImpl {
+final class ListSelectedValuePropertyImpl {
     private static final ListSelectionListener SELECTION_LISTENER = e -> {
         JList list = (JList) e.getSource();
         Object selectedValue = list.getSelectedValue();

src/main/java/io/github/parubok/fxprop/SwingPropertySupport.java

@@ -245,7 +245,17 @@ public static <E> ObjectProperty<E> selectedItemProperty(JComboBox<E> comboBox)
      * @implNote The property always passes {@code false} as a value of {@code shouldScroll} argument of {@link JList#setSelectedValue(Object, boolean)}.
      */
     public static <E> ObjectProperty<E> selectedValueProperty(JList<E> list) {
-        return SelectedValuePropertyImpl.getProperty(list);
+        return ListSelectedValuePropertyImpl.getProperty(list);
+    }
+
+    /**
+     * @param list List component. Not null.
+     * @return Integer property for 'selectedIndex' property of the specified list. Value {@code -1} of the property means no selection.
+     * @see JList#setSelectedIndex(int)
+     * @see JList#getSelectedIndex()
+     */
+    public static IntegerProperty selectedIndexProperty(JList<?> list) {
+        return ListSelectedIndexPropertyImpl.getProperty(list);
     }
 
     /**

src/test/java/io/github/parubok/fxprop/SelectedIndexPropertyTest.java

@@ -0,0 +1,35 @@
+package io.github.parubok.fxprop;
+
+import io.github.parubok.swingfx.beans.property.IntegerProperty;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import javax.swing.DefaultListModel;
+import javax.swing.JList;
+import javax.swing.SwingUtilities;
+
+class SelectedIndexPropertyTest {
+    @Test
+    public void basicTest() throws Exception {
+        SwingUtilities.invokeAndWait(() -> {
+            DefaultListModel<String> model = new DefaultListModel<>();
+            model.addElement("a1");
+            model.addElement("b2");
+            model.addElement("c3");
+            JList<String> list = new JList<>();
+            list.setModel(model);
+
+            IntegerProperty p = SwingPropertySupport.selectedIndexProperty(list);
+            Assertions.assertEquals(-1, list.getSelectedIndex());
+            Assertions.assertEquals(-1, p.getValue());
+
+            list.setSelectedIndex(1);
+            Assertions.assertEquals(1, list.getSelectedIndex());
+            Assertions.assertEquals(1, p.getValue());
+
+            list.clearSelection();
+            Assertions.assertEquals(-1, list.getSelectedIndex());
+            Assertions.assertEquals(-1, p.getValue());
+        });
+    }
+}