需要幫助修復NullPointerException

Question

這是hang子手。當我運行代碼時，我得到了一些空指針異常，並不知道如何解決這個問題。

這是編譯錯誤究竟說的話：

Exception in thread "main" 
java.lang.NullPointerException at 
hangmanrevised.createGame(hangmanrevised.java:66) 
at 
hangmanrevised.<init>(hangmanrevised.java:35) 
at 
hangmanrevised.main(hangmanrevised.java:202) 

任何幫助表示讚賞。

import java.awt.*; 
import java.awt.event.*; 
import java.util.Random; 
import java.lang.reflect.Array; 
import javax.swing.*; 


public class hangmanrevised extends JFrame implements ActionListener { 

    private int wrongs; 
    private String right; 
    private StringBuffer guess; 
    private TextField Letter; 
    private String message; 
    private String information; 
    private JButton button; 
    private final int hung = 11; 


    public hangmanrevised() { 
    setSize(600,400); 
    setLocationRelativeTo(null); 
    setDefaultCloseOperation(EXIT_ON_CLOSE); 
    setLayout(new FlowLayout()); 

    ImageIcon background = new ImageIcon("nightsky.png"); 
    TextField Letter = new TextField(); 
    JLabel label = new JLabel("pick a Letter"); 
    Button button = new Button("Enter"); 
    add(label); 
    add(button); 
    add(Letter); 

    button.addActionListener(this); 

    createGame(); 
    } 



    public void createGame(){ 

     wrongs = 0; 

     String word = "school|java|programming|science|computer"; 
     String[] temp; 

     String delimiter = "\\|"; 

     temp = word.split(delimiter); 

     Random randomPicker = new Random(); 


     int randomWord = randomPicker.nextInt(temp.length); 

     right = new String(temp[randomWord]); 

     char positions[] = new char[right.length()]; 
     for (int i = 0; i < right.length(); i++) { 
     positions[i] = '-'; 

     } 
     String s = new String(positions); 
     guess = new StringBuffer(s); 

     Letter.setText(""); 

     message=""; 
     information = ""; 
     repaint(); 
     } 



    public void paint(Graphics g) { 
     super.paint(g); 
      //g.drawImage(background, 0, 156, Color.green, Enter); 


     int baseY = 350; 
     g.setColor(Color.lightGray); 
      g.drawRect(0, baseY,400,baseY); 
     g.fillRect(0, baseY,400,baseY); 

      g.setColor(Color.darkGray); 
      //g.drawRect(250,50,125,50); 
      //g.fillRect(250,50,125,50); 

     if (wrongs > 0){ 
     g.drawLine(125,baseY,125,baseY-100); 
     g.drawLine(123,baseY,123,baseY-100); 
     } 
     if (wrongs > 1){ 
     g.drawLine(110,baseY,125,baseY-15); 
     g.drawLine(108,baseY,122,baseY-15); 
     } 
     if (wrongs > 2){ 
     g.drawLine(140,baseY,125,baseY-15); 
     g.drawLine(138,baseY,122,baseY-15); 
     } 
     if (wrongs > 3){ 
     g.drawLine(125,baseY-100,175,baseY-100); 
     g.drawLine(125,baseY-98,175,baseY-98); 
     } 
     if (wrongs > 4){ 
     g.drawLine(175,baseY-100,175,baseY-75); 
     } 
     if (wrongs > 5){ 
     g.drawOval(170,baseY-75,10,12); 
     } 
     if (wrongs > 6){ 
     g.drawOval(160,baseY-65,15,25); 
     g.fillOval(160,baseY-65,15,25); 
     } 
     if (wrongs > 7){ 
     g.drawLine(150,baseY-65,170,baseY-60); 
     } 
     if (wrongs > 8){ 
     g.drawLine(173,baseY-60,193,baseY-65); 
     } 
     if (wrongs > 9){ 
     g.drawLine(155,baseY-30,170,baseY-45); 
     } 
     if (wrongs > 10){ 
     g.drawLine(173,baseY-45,193,baseY-30); 
     } 


     g.drawString(message, 60, baseY+25); 
     g.drawString(information, 25, baseY+45); 
     g.drawString(new String (guess), 110, 60); 
     //listener(); 
     } 

public void actionPerformed(ActionEvent e){ 

     if (e.getSource() == button){ 

     processTurn(); 

     Letter.setText(""); 
     repaint(); 
     } 
     } 

    private void processTurn(){ 
     String s, t; 
     char a; 

     s = Letter.getText(); 
     a = s.charAt(0); 

     if (!Character.isLetter(a)){ 
     message="Letters only"; 
     return; 
     } 
     if (s.length()>1){ 
     message="Enter 1 letter only"; 
     return; 
     } 

     t = new String(guess); 
     if (t.indexOf(s) != -1){ 
     JOptionPane.showMessageDialog(null, "LETTER USED ALREADY"); 

     return; 
     } 



     if (right.indexOf(s) == -1){ 
     message=""; 
     wrongs++; 
     if (wrongs == hung){ 
     JOptionPane.showMessageDialog(null, "YOU LOST!"); 


     } 

     return; 
     } 

     for (int i = 0; i < right.length(); i++){ 
     if (right.charAt(i) == a){ 
     guess.setCharAt(i, a); 
     } 
     } 
     t = new String(guess); 


     if (t.indexOf('-') == -1){ 
     JOptionPane.showMessageDialog(null, "YOU WIN!"); 
     message="You win!"; 
     return; 
     } 

     message=""; 
     repaint(); 
     } 

    public static void main(String[] args) { 
     hangmanrevised f = new hangmanrevised(); 
     f.setVisible(true); 

    } 
} 

Answer 1

嘗試使用「|」爲您的分隔符
看BalusC評論。能夠以簡單的形式提出問題並運行調試器很重要。

Answer 2

在構造函數中，您意外地將new TextField()分配給局部變量而不是該字段。

變化

TextField Letter = new TextField(); 

到

Letter = new TextField(); 

---

順便說一句，我強烈建議你用大寫，即小寫和類名開始你的變量，

• letter而不是Letter和
• HangmanRevised，而不是hangmanrevised