使用事件處理程序找不到符號錯誤

Question

我無法正確初始化變量。之前我得到一個數字格式異常，因爲我正在解析一個空文本字段內的整數。現在我創建了一個if語句，首先檢查該字段是否爲空，然後解析其中的整數。我現在遇到的問題是我的事件處理程序無法識別變量，因爲它在if語句中。我試圖在if語句之外聲明它，但那也不起作用。任何提示指向我在正確的方向？這裏是我的代碼：

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); 
    } 
} 

Answer 1

如果str爲空時，您的代碼可以接受的行爲，您需要定義express默認值如果是這樣的話。如果默認值分別爲-1，例如，你會怎麼做：

int express = (str != null && !"".equals(str)) ? Integer.parseInt(str) : -1; 

再後來，就應該相應地對待-1情況。

你需要像這樣初始化express，所以它是有效的，可以在lambda表達式中使用。

Answer 2

而不是

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

嘗試

final int express = (tfExpress.getText() != null && !tfExpress.getText().equals("")) : Integer.parseInt(str) : 0;