FULL PRODUCT VERSION :
java version "1.8.0_60"
Java(TM) SE Runtime Environment (build 1.8.0_60-b27)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b23, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.3.9600]

A DESCRIPTION OF THE PROBLEM :
When a range selection is made in an table with a multiple selection model, getSelectedIndices may contain -1 values.
First select a row for instance the third. then expand the selection to a row with an higher row nummer (f.e. the forth), then expand the selection to the first row. 
GetSelectedIndices contains now 0, -1, 2 instead of 0,1,2.

REGRESSION.  Last worked in version 8u51

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
create a table. set table.getSelectionModel().setSelectionMode(SelectionMode.MULTIPLE);
add a couple rows (5 or more)

select the second row. (click on the second row)
expand the selection to the third row (hold down shift-key click on the third row)
expand the selection to the first row (hold down shift-key click on the first row)



EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
the selected Indices ( table.getSelectionModel().getSelectedIndices()) should contain 0,1,2
ACTUAL -
the selected Indices contains 0,-1,2

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------


import javafx.application.Application;
import javafx.beans.property.SimpleStringProperty;
import javafx.collections.FXCollections;
import javafx.collections.ListChangeListener.Change;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.SelectionMode;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.Pane;
import javafx.scene.layout.VBox;
import javafx.scene.text.Font;
import javafx.stage.Stage;

public class FxTableSelectionTest extends Application {

   final ScrollPane sp = new ScrollPane();
   // @formatter:off 
   private static final ObservableList<Person> data =         
         FXCollections.observableArrayList(
             
             new Person("Astrid", "G��rtner"),
             new Person("Holger", "G��rtner"),
             new Person("Theo", "G��rtner"),
             new Person("Klaus", "G��rtner"),
             new Person("Sigrid", "G��rtner")
             
         );

   // @formatter:on 
   @Override
   public void start(Stage stage) {
      final Label label = new Label("Address Book");
      label.setFont(new Font("Arial", 20));
      Pane main = new VBox();
      TableView table = createTable();
      main.getChildren().addAll(label, table);
      Scene scene = new Scene(main);
      stage.setScene(scene);
      stage.setTitle("Test");

      stage.show();

   }
   @SuppressWarnings({ "rawtypes", "unchecked" })
   public static TableView createTable() {
      final TableView table = new TableView();
      table.setEditable(false);

      TableColumn firstNameCol = new TableColumn("First Name");
      firstNameCol.setCellValueFactory(new PropertyValueFactory<Object, Object>("firstName"));
      firstNameCol.setPrefWidth(200);
      TableColumn lastNameCol = new TableColumn("Last Name");
      lastNameCol.setCellValueFactory(new PropertyValueFactory<>("lastName"));
      lastNameCol.setPrefWidth(200);
      table.setItems(data);
      table.getColumns().addAll(firstNameCol, lastNameCol);

      table.getSelectionModel().setSelectionMode(SelectionMode.MULTIPLE);
      table.getSelectionModel().getSelectedIndices().addListener(FxTableSelectionTest::selectionChanged);
      return table;
   }

   private static void selectionChanged(Change<? extends Object> c) {
      while (c.next()) {
         System.out.println("Selection changed: " + c.getList());
      }
   }

   public static void main(String[] args) {
      launch(args);
      setUserAgentStylesheet(STYLESHEET_MODENA);
   }



   public static class Person {

      private final SimpleStringProperty firstName;
      private final SimpleStringProperty lastName;

      private Person(String fName, String lName) {
         this.firstName = new SimpleStringProperty(fName);
         this.lastName = new SimpleStringProperty(lName);
      }

      public String getFirstName() {
         return firstName.get();
      }

      public void setFirstName(String fName) {
         firstName.set(fName);
      }

      public String getLastName() {
         return lastName.get();
      }

      public void setLastName(String fName) {
         lastName.set(fName);
      }

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

CUSTOMER SUBMITTED WORKAROUND :
use this to get the selected indices 

   /**
    * gets the selected indices from the selected Cells, which are the selection model's 
    * 'proper' internal data structure, selectedItems and selectedIndices are both 'read-only and unbacked'.
    * and due to a bug in jdk1.8.0_60 selectedIndices does not work properly in all cases
    * @return the list of indices of the selected rows
    */
   private List<Integer> getSelectedIndices() {
      Set<Integer> selectedRows = new HashSet<Integer>();
      List<TablePosition> selectedCells = m_FxTable.getSelectionModel().getSelectedCells();
      selectedCells.forEach(tablePosition -> {
         selectedRows.add(tablePosition.getRow());
      });
      return new ArrayList<>(selectedRows);
   }