Cannot Find Symbol Error with event handler

I am having trouble trying to initialize a variable correctly. Earlier I was getting a Number Format Exception because I was parsing an integer inside of an empty text field. Now I have created an if statement that checks first to see if the field is empty, then parses an integer inside of it. The problem i'm having now is that my event handler can't recognize the variable, because it is inside the if statement. I tried declaring it outside of the if statement but that didn't work either. Any tips to point me in the right direction? Here is my code:

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.image.Image;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Pane;
import javafx.stage.Stage;

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedList;
import java.util.concurrent.atomic.AtomicReference;

public class Main extends Application {

   @Override
   public void start(Stage primaryStage) {

      ArrayList<Integer> deck;
      deck = new ArrayList<>();
      int i = 1;
      while(i < 52){
         deck.add(i);
         i++;
      }
      final AtomicReference<String> result = new AtomicReference<>("go.");

      Collections.shuffle(deck);

      BorderPane pane = new BorderPane();

      HBox top = new HBox(10);
      Label display = new Label(result.toString());
      Button btShuffle = new Button("Shuffle");
      btShuffle.setOnAction(
            e -> {
               Collections.shuffle(deck);
            });
      top.getChildren().add(display);
      top.getChildren().add(btShuffle);

      HBox center = new HBox(10);
      Card card1 = new Card(deck.get(0));
      center.getChildren().add(card1);

      Card card2 = new Card(deck.get(1));
      center.getChildren().add(card2);

      Card card3 = new Card(deck.get(2));
      center.getChildren().add(card3);

      Card card4 = new Card(deck.get(3));
      center.getChildren().add(card4);

      HBox bottom = new HBox(10);
      Label expression = new Label("Please Enter the expression: ");

      TextField tfExpress = new TextField();
      LinkedList<Object> expInput = new LinkedList<>();
      ArrayList<Character> signs = new ArrayList<>();
      signs.add('/');
      signs.add('+');
      signs.add('(');
      signs.add(')');
      signs.add('-');
      signs.add('^');
      signs.add('*');
      signs.add('%');
      String str = tfExpress.getText();
      char tempStor[] = str.toCharArray();
      for(char c: tempStor){
         expInput.add(c);
      }

      if(tfExpress.getText() != null && tfExpress.getText().equals(""))
      {
         int express = Integer.parseInt(str);
      }

      expInput.removeIf(p-> p.equals(signs));

      Button btVerify = new Button("Verify");
      btVerify.setOnAction(
            (ActionEvent e) -> {
               if(card1.CardValue() == (int)expInput.get(0)
               && card2.CardValue() == (int)expInput.get(1)
               && card3.CardValue() == (int)expInput.get(2)
               && card4.CardValue() == (int)expInput.get(3)){
                  if(express == 24){
                     result.set("Correct");
                  }
                  else
                     result.set("Incorrect");

               }
               else
                  result.set("The numbers in the expression don't "
                     + "match the numbers in the set.");
            });

      pane.setTop(top);
      pane.setCenter(center);
      pane.setBottom(bottom);

      Scene scene = new Scene(pane);
      primaryStage.setTitle("24 card game");
      primaryStage.setScene(scene);
      primaryStage.show();
   }

   public class Card extends Pane {
      public int cardVal;
      Card(int card){
         Image cardImage;
         cardImage = new Image("card/"+ card +".png");
         cardVal = card;
      }

      public int CardValue(){
         int card = 0;

         if(cardVal <= 13){
            card = cardVal;
         }
         else if(cardVal > 13 && cardVal <= 26){
            card = cardVal - 13;
         }
         else if(cardVal > 26 && cardVal <= 39){
            card = cardVal - 26;
         }
         else if(cardVal > 39 && cardVal <= 52){
            card = cardVal - 39;
         }         
         return card;
      }
   }
   public static void main(String[] args) {
      launch(args);
   }
}