Javafx - imprimindo contador de inteiros

//IMPRIMINDO CONTADOR DE INTEIROS

import javafx.application.Application;

import javafx.scene.Node;

import javafx.scene.Scene;

import javafx.scene.canvas.Canvas;

import javafx.scene.canvas.GraphicsContext;

import javafx.scene.control.Button;

import javafx.stage.Stage;

import javafx.scene.paint.Color;

import javafx.scene.input.KeyCode;

import javafx.scene.layout.Pane;

import javafx.scene.text.Font;

import javafx.scene.text.FontWeight;

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

public class PROJETO extends Application {

     public static int TAM = 100;

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

     static GraphicsContext ctx = canvas.getGraphicsContext2D ( );

     static Pane ro_ot = new Pane ( );

     static Scene sce_ne = new Scene ( ro_ot, 620, 350 );

     static Button btn_1 = new Button ( "FECHAR" );

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

     public static Node But_ton_3 ( ) {

         btn_1.setPrefWidth ( 100 );// Largura do botão

         btn_1.setLayoutX ( 267 );// Posição do botão coluna

         btn_1.setPrefHeight ( 20 );// altura do botão

         btn_1.setLayoutY ( 300 );// //Posição do botão linha       

         btn_1.setStyle ( "-fx-padding: 1;" + "-fx-border-style: solid inside;"

                   + "-fx-border-width: 2;" + "-fx-border-insets: 1;"

                   + "-fx-border-radius: 1;" + "-fx-border-color: blue;"

                   + "-fx-font-style: italic;"

                   + "-fx-font-family: Consolas;"

                   );  

         btn_1.setOnKeyPressed ( e -> {

              if ( e.getCode ( ) == KeyCode.ENTER ) {

                   System.exit ( 0 );

              }

         } );

         return btn_1;

     }

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

     public static void Arr ( ) {

         String st = " ";

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

         ctx.setFill ( Color.BLUE );

         ctx.fillText ( "Imprimindo abaixo o contador de inteiros", 190, 80 );

         ctx.setFont ( Font.font ( "Arial", FontWeight.BOLD, 14 ) );

         ctx.setFill ( Color.BLACK );

         int i = 0;

         do {

              if ( i % 10 == 0 ){

                   st += "\n";

              }

              if ( i >= 0 && i <= 9 )

                   st += ( "0" );

              st += i + "    ";

              i++;

         } while ( i < 100 );

         ctx.setFill ( Color.MAGENTA );

         ctx.fillText ( st, 150, 100 );      

     }

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

     public void start ( Stage stage ) {

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

         stage.setTitle ( "IMPRIMINDO CONTADOR DE INTEIROS" );

         //Criando moldura e dando efeitos

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

                   + "-fx-border-width: 18;" + "-fx-border-insets: 5;"

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

         ctx.setFill ( Color.RED );

         ctx.fillText ( "IMPRIMINDO CONTADOR DE INTEIROS", 190, 50 );

         Arr ( );

         But_ton_3 ( );

         ro_ot.getChildren ( ).addAll ( canvas, btn_1 );

         stage.setScene ( sce_ne );

         stage.show ( );

     }

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

     public static void main ( String [ ] args ) {

         Application.launch ( args );

     }

}