Javafx - obtendo valores em listview

Um objeto ListView apresenta ao usuário uma lista
de rolagem de itens de texto,  estas rolagens podem
ser orientadas horizontalmente ou verticalmente 
como é nosso caso.
Apresento aqui um exemplo de como obter 
cada item do ListView individualmente.

Veja abaixo uma imagem do programa em execução:

 Veja abaixo o código do programa:

import javafx.application.Application;

import javafx.beans.value.ChangeListener;

import javafx.beans.value.ObservableValue;

import javafx.collections.FXCollections;

import javafx.collections.ObservableList;

import javafx.geometry.Insets;

import javafx.scene.Scene;

import javafx.scene.canvas.Canvas;

import javafx.scene.canvas.GraphicsContext;

import javafx.scene.control.ListView;

import javafx.scene.layout.GridPane;

import javafx.scene.layout.Pane;

import javafx.scene.paint.Color;

import javafx.scene.text.Font;

import javafx.scene.text.FontWeight;

import javafx.stage.Stage;

public class PROJETO extends Application {

     static int i;

     static String str = "";

     static String str1 = "";

     static String [ ] st = { "Um", "Dois", "Tres", "Quatro", "Cinco", "Seis",

         "Sete", "Oito", "Nove", "Dez", "Onze", "Doze", "Viva_Java" };

     static ObservableList < String > numeros_1 = FXCollections

              .observableArrayList ( st );

     static ListView < String > numListView_1 = new ListView <> ( numeros_1 );

     static Pane root = new Pane ( );

     static Canvas canvas = new Canvas ( 620, 350 );

     static GraphicsContext ctx = canvas.getGraphicsContext2D ( );

     static Scene scene = new Scene ( root, 620, 350, Color.WHITE );

     static GridPane grid_1 = new GridPane ( );

     // /////////////////////////////////////////////////////////////////////////

     public static void List_View_1 ( ) {

         numListView_1.getSelectionModel ( ).selectedIndexProperty ( )

         .addListener ( new ChangeListener < Number > ( ) {

              @SuppressWarnings ( "rawtypes" )

              public void changed ( ObservableValue ov, Number value,

                        Number new_value ) {

                   str = st [ new_value.intValue ( ) ];

                   str1 = "";

                   // Coluna, linha, comprimento, altura

                   ctx.clearRect ( 270, 100, 400, 50 );

                   ctx.clearRect ( 270, 130, 500, 50 );

                   ctx.clearRect ( 270, 160, 500, 50 );

                   ctx.setFont ( Font.font ( "Arial", FontWeight.NORMAL,15 ) );                            

                   i = new_value.intValue ( );

                   ctx.setFill ( Color.BLACK );

                   ctx.fillText ( "Palavra => ", 290, 120 );

                   ctx.setFill ( Color.RED );

                   ctx.fillText ( " " + str, 370, 120 );

                   ctx.setFill ( Color.BLACK );

                   ctx.fillText ( "Abaixo a string indexada", 290, 150 );

                   ctx.setFill ( Color.RED );

                   for ( i = 0; i < str.length ( ); ++i ) {

                        char c = str.charAt ( i );

                        str1 += c + "  ";

                   }          

                   int quant = 0;

                   for ( int i = 0; i < str.length ( ); i++ )

                        if ( str.charAt ( i ) != ' ' )

                            quant++;

                   ctx.setFill ( Color.RED );

                   ctx.fillText ( str1, 290, 180 );

                   System.out.println ( quant );

                   ctx.setFill ( Color.BLUE );

                   ctx.fillText ( "A string tem ", 290, 210 );           

                   ctx.setFill ( Color.RED );

                   ctx.fillText ( " " + quant, 375, 210 );

                   ctx.setFill ( Color.BLUE );

                   ctx.fillText ( "caracteres", 395, 210 ); 

              }            

         } );

         grid_1.setHgap ( 10 );

         grid_1.setVgap ( 50 );

         grid_1.setPadding ( new Insets ( 5 ) );

         //Largura máximo do ListView

         numListView_1.setPrefWidth ( 200 );

         //Altura máxima do ListView

         numListView_1.setPrefHeight ( 120 );

         numListView_1.setStyle ( "-fx-padding: 5;" + "-fx-border-style: solid inside;"

                   + "-fx-border-width: 2;" + "-fx-border-insets: 5;"

                   + "-fx-border-radius: 5;" + "-fx-border-color: red;" );

         grid_1.add ( numListView_1, 5, 2 );

         root.getChildren ( ).add ( grid_1 );

     }

     // /////////////////////////////////////////////////////////////////////////

     @Override

     public void start ( Stage stage ) {

         ctx.setFont ( Font.font ( "Arial", FontWeight.NORMAL, 15 ) );

         stage.setTitle ( "JAVAFX - OBTENDO VALORES EM LISTVIEW" );

         //Criando moldura e dando efeitos

         root.setStyle ( "-fx-padding: 5;" + "-fx-border-style: solid inside;"

                   + "-fx-border-width: 12;" + "-fx-border-insets: 5;"

                   + "-fx-border-radius: 5;" + "-fx-border-color: red;" );

         ctx.setFill ( Color.RED );

         ctx.fillText ( "JAVAFX - OBTENDO VALORES EM LISTVIEW", 140, 50 );

         ctx.setFill ( Color.BLUE );

         ctx.fillText ( "Escolha uma palavra no listview", 190, 80 );

         root.getChildren ( ).addAll ( canvas );

         List_View_1 ( );      

         stage.setScene ( scene );

         stage.show ( );

     }

     // /////////////////////////////////////////////////////////////////////////

     public static void main ( String [ ] args ) {

         launch ( args );

     }

}