Java Swing jLabel java.lang.NullPointerException

124

惠特龙：

我有一个班级的Hangman和一个班级的GUI。子手课的过程。因此，我想将String Hangman类的值String传递给GUI中的jLabel。当我运行该项目时，即使我编写了正确的代码，也遇到了java.lang.NullPointerException。用户单击开始时。Hangman类的值将显示给jLabel

子手班

package hangman;
import java.util.*;
import java.io.*;
import java.awt.*;

public class Hangman {
    
    String filename = "words.txt";
    String[] wordList;
    String[] wordBanks = {"DISAVOW","KEYHOLE","QUIZZES",
        "WHOMEVER","ZIGZIG","WHEEZY","UNWORTHY",
        "WHIZZING","JOCKEY","MICROWAVE"};
    String[] answer;
    int index;
    String[] resultarray;
    StringBuilder stringbuilder = new StringBuilder();
    String resultstring;
    
    public Hangman()
    {
        initialComponent();
    }
    
    public void initialComponent()
    {
        index = randomIndex();
        answer = wordBanks[index].split("");
        resultarray = new String[answer.length];
        for(int i = 0; i < answer.length ;i++)
        {
            resultarray[i] = " _ ";
            stringbuilder.append(resultarray[i]);
        }
        resultstring = stringbuilder.toString();
    }
    
    public int randomIndex()
    {
        int rand = 0;
        // define the range 
        int max = 10; 
        int min = 0; 
        int range = max - min; 
  
        // generate random numbers within 1 to 10 
        for (int i = 0; i < 10; i++) { 
            rand = (int)(Math.random() * range) + min; 
  
            // Output is different everytime this code is executed 
            //System.out.println(rand); 
        } 
        
        return rand;
    }
    
    public void printWord()
    {
        System.out.println(wordBanks[randomIndex()].toString() + "|" + wordBanks[randomIndex()].length());
    }
    
    public void initialWord()
    {
        int random = randomIndex();
        //answer = new String[random];
        answer = wordBanks[random].split("");
        for (int i = 0; i < answer.length;i++)
            System.out.println(answer[i]);
    }
    
    
    

    
   
    public static void main(String[] args) {
        // TODO code application logic here
        Hangman hangman = new Hangman();
        GUI gui = new GUI();
        gui.setVisible(true);
        
        
       
    }
    
}

GUI类 '''

package hangman;

public class GUI extends javax.swing.JFrame {

    Hangman hangman;
    
    
    
    /**
     * Creates new form GUI
     */
    public GUI() {
        initComponents();
        //defaultResult();
    }
    
    public void defaultResult()
    {
        
        jLabelGuess.setText(hangman.resultstring);
    }
    

   
    @SuppressWarnings("unchecked")
                  
    private void initComponents() {

        jFrame1 = new javax.swing.JFrame();
        jLabel1 = new javax.swing.JLabel();
        jButtonStart = new javax.swing.JButton();
        jButtonA = new javax.swing.JButton();
        jButtonB = new javax.swing.JButton();
        jButtonC = new javax.swing.JButton();
        jButtonD = new javax.swing.JButton();
        jButtonE = new javax.swing.JButton();
        jButtonF = new javax.swing.JButton();
        jButtonG = new javax.swing.JButton();
        jButtonH = new javax.swing.JButton();
        jButtonI = new javax.swing.JButton();
        jButtonJ = new javax.swing.JButton();
        jButtonO = new javax.swing.JButton();
        jButtonP = new javax.swing.JButton();
        jButtonQ = new javax.swing.JButton();
        jButtonR = new javax.swing.JButton();
        jButtonK = new javax.swing.JButton();
        jButtonS = new javax.swing.JButton();
        jButtonL = new javax.swing.JButton();
        jButtonT = new javax.swing.JButton();
        jButtonN = new javax.swing.JButton();
        jButtonM = new javax.swing.JButton();
        jPanel1 = new javax.swing.JPanel();
        jButtonO1 = new javax.swing.JButton();
        jButtonP1 = new javax.swing.JButton();
        jButtonK1 = new javax.swing.JButton();
        jButtonL1 = new javax.swing.JButton();
        jButtonN1 = new javax.swing.JButton();
        jButtonM1 = new javax.swing.JButton();
        jLabel2 = new javax.swing.JLabel();
        jLabelAtemp = new javax.swing.JLabel();
        jLabelGuess = new javax.swing.JLabel();

        javax.swing.GroupLayout jFrame1Layout = new javax.swing.GroupLayout(jFrame1.getContentPane());
        jFrame1.getContentPane().setLayout(jFrame1Layout);
        jFrame1Layout.setHorizontalGroup(
            jFrame1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 400, Short.MAX_VALUE)
        );
        jFrame1Layout.setVerticalGroup(
            jFrame1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 300, Short.MAX_VALUE)
        );

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jLabel1.setFont(new java.awt.Font("Tahoma", 0, 24)); // NOI18N
        jLabel1.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
        jLabel1.setText("Welcome to Hangman");

        jButtonStart.setText("Start");
        jButtonStart.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonStartActionPerformed(evt);
            }
        });

        jButtonA.setText("A");

        jButtonB.setText("B");

        jButtonC.setLabel("C");

        jButtonD.setText("D");
        jButtonD.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonDActionPerformed(evt);
            }
        });

        jButtonE.setText("E");

        jButtonF.setText("F");

        jButtonG.setText("G");

        jButtonH.setText("H");
        jButtonH.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonHActionPerformed(evt);
            }
        });

        jButtonI.setText("I");

        jButtonJ.setText("J");
        jButtonJ.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonJActionPerformed(evt);
            }
        });

        jButtonO.setText("O");
        jButtonO.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonOActionPerformed(evt);
            }
        });

        jButtonP.setText("P");

        jButtonQ.setText("Q");

        jButtonR.setText("R");

        jButtonK.setText("K");
        jButtonK.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonKActionPerformed(evt);
            }
        });

        jButtonS.setText("S");
        jButtonS.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonSActionPerformed(evt);
            }
        });

        jButtonL.setText("L");

        jButtonT.setText("T");

        jButtonN.setText("N");
        jButtonN.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonNActionPerformed(evt);
            }
        });

        jButtonM.setText("M");

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 256, Short.MAX_VALUE)
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 0, Short.MAX_VALUE)
        );

        jButtonO1.setText("O");
        jButtonO1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonO1ActionPerformed(evt);
            }
        });

        jButtonP1.setText("P");

        jButtonK1.setText("K");
        jButtonK1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonK1ActionPerformed(evt);
            }
        });

        jButtonL1.setText("L");

        jButtonN1.setText("N");
        jButtonN1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonN1ActionPerformed(evt);
            }
        });

        jButtonM1.setText("M");

        jLabel2.setText("Atemps left:");

        jLabelAtemp.setText("jLabel3");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                            .addContainerGap()
                            .addComponent(jButtonN1, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                            .addComponent(jButtonO1, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                            .addComponent(jButtonP1, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addGap(189, 189, 189))
                        .addGroup(layout.createSequentialGroup()
                            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                .addGroup(layout.createSequentialGroup()
                                    .addGap(57, 57, 57)
                                    .addComponent(jButtonK1, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                    .addComponent(jButtonL1, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                    .addComponent(jButtonM1, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE))
                                .addGroup(layout.createSequentialGroup()
                                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                                        .addGroup(layout.createSequentialGroup()
                                            .addComponent(jButtonA, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(jButtonB, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(jButtonC, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(jButtonD, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE))
                                        .addGroup(layout.createSequentialGroup()
                                            .addComponent(jButtonK, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(jButtonL, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(jButtonM, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                                            .addComponent(jButtonN, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)))
                                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                    .addComponent(jButtonO, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                    .addComponent(jButtonP, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                    .addComponent(jButtonQ, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                    .addComponent(jButtonR, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                    .addComponent(jButtonS, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                    .addComponent(jButtonT, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE))
                                .addGroup(layout.createSequentialGroup()
                                    .addGap(163, 163, 163)
                                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                                        .addComponent(jLabelGuess, javax.swing.GroupLayout.PREFERRED_SIZE, 287, javax.swing.GroupLayout.PREFERRED_SIZE)
                                        .addGroup(layout.createSequentialGroup()
                                            .addComponent(jButtonE, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(jButtonF, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(jButtonG, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(jButtonH, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)))
                                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                    .addComponent(jButtonI, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)
                                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                    .addComponent(jButtonJ, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE)))
                            .addGap(18, 18, 18)))
                    .addGroup(layout.createSequentialGroup()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(layout.createSequentialGroup()
                                .addGap(192, 192, 192)
                                .addComponent(jLabel1))
                            .addGroup(layout.createSequentialGroup()
                                .addGap(20, 20, 20)
                                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                                    .addComponent(jLabel2)
                                    .addComponent(jButtonStart))
                                .addGap(18, 18, 18)
                                .addComponent(jLabelAtemp)))
                        .addGap(155, 155, 155)))
                .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                        .addComponent(jLabel1)
                        .addGap(35, 35, 35)
                        .addComponent(jLabelGuess, javax.swing.GroupLayout.PREFERRED_SIZE, 25, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 37, Short.MAX_VALUE)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jButtonA)
                            .addComponent(jButtonB)
                            .addComponent(jButtonC)
                            .addComponent(jButtonD)
                            .addComponent(jButtonE)
                            .addComponent(jButtonF)
                            .addComponent(jButtonG)
                            .addComponent(jButtonH)
                            .addComponent(jButtonI)
                            .addComponent(jButtonJ))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jButtonK)
                            .addComponent(jButtonL)
                            .addComponent(jButtonM)
                            .addComponent(jButtonO)
                            .addComponent(jButtonP)
                            .addComponent(jButtonQ)
                            .addComponent(jButtonR)
                            .addComponent(jButtonS)
                            .addComponent(jButtonT)
                            .addComponent(jButtonN))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jButtonK1)
                            .addComponent(jButtonL1)
                            .addComponent(jButtonM1)
                            .addComponent(jButtonO1)
                            .addComponent(jButtonP1)
                            .addComponent(jButtonN1))
                        .addGap(28, 28, 28)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel2)
                            .addComponent(jLabelAtemp))
                        .addGap(29, 29, 29)
                        .addComponent(jButtonStart)))
                .addGap(19, 19, 19))
        );

        pack();
    }// </editor-fold>                        

    private void jButtonDActionPerformed(java.awt.event.ActionEvent evt) {                                         
       
    }                                        

    private void jButtonHActionPerformed(java.awt.event.ActionEvent evt) {                                         
        
    }                                        

    private void jButtonJActionPerformed(java.awt.event.ActionEvent evt) {                                         
        
    }                                        

    private void jButtonOActionPerformed(java.awt.event.ActionEvent evt) {                                         
        
    }                                        

    private void jButtonSActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jButtonNActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jButtonKActionPerformed(java.awt.event.ActionEvent evt) {                                         
      
    }                                        

    private void jButtonO1ActionPerformed(java.awt.event.ActionEvent evt) {                                          
        // TODO add your handling code here:
    }                                         

    private void jButtonK1ActionPerformed(java.awt.event.ActionEvent evt) {                                          
       
    }                                         

    private void jButtonN1ActionPerformed(java.awt.event.ActionEvent evt) {                                          
       
    }                                         

    private void jButtonStartActionPerformed(java.awt.event.ActionEvent evt) {                                             
        // TODO add your handling code here:
        jLabelGuess.setText(hangman.resultstring);
    }                                            

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(GUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(GUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(GUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(GUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>
        //Hangman hangman = new Hangman();
        //GUI gui = new GUI();
        //gui.setVisible(true);
        /* Create and display the form */
        /*java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
         
                new GUI().setVisible(true);
            }
        });*/
        
        
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButtonA;
    private javax.swing.JButton jButtonB;
    private javax.swing.JButton jButtonC;
    private javax.swing.JButton jButtonD;
    private javax.swing.JButton jButtonE;
    private javax.swing.JButton jButtonF;
    private javax.swing.JButton jButtonG;
    private javax.swing.JButton jButtonH;
    private javax.swing.JButton jButtonI;
    private javax.swing.JButton jButtonJ;
    private javax.swing.JButton jButtonK;
    private javax.swing.JButton jButtonK1;
    private javax.swing.JButton jButtonL;
    private javax.swing.JButton jButtonL1;
    private javax.swing.JButton jButtonM;
    private javax.swing.JButton jButtonM1;
    private javax.swing.JButton jButtonN;
    private javax.swing.JButton jButtonN1;
    private javax.swing.JButton jButtonO;
    private javax.swing.JButton jButtonO1;
    private javax.swing.JButton jButtonP;
    private javax.swing.JButton jButtonP1;
    private javax.swing.JButton jButtonQ;
    private javax.swing.JButton jButtonR;
    private javax.swing.JButton jButtonS;
    private javax.swing.JButton jButtonStart;
    private javax.swing.JButton jButtonT;
    private javax.swing.JFrame jFrame1;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabelAtemp;
    private javax.swing.JLabel jLabelGuess;
    private javax.swing.JPanel jPanel1;
    // End of variables declaration                   
}

运行应用程序时出现消息错误。

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at hangman.GUI.jButtonStartActionPerformed(GUI.java:400)
    at hangman.GUI.access$000(GUI.java:12)
    at hangman.GUI$1.actionPerformed(GUI.java:96)

德雷克·利亚姆（DrakeLiam）：

在GUI类中，仅声明即可Hangman hangman，这意味着从未调用过Hangman类来执行或初始化任何值。因此，hangman.resultstring调用时为null jLabelGuess.setText(hangman.resultstring)，因为resultstring值是从Hangman类获取的；并在jLabelGuess.setText()和函数上导致Null Pointer Exception错误jButtonStartActionPerformed()

如果初始化刽子手类你可以解决它：Hangman hangman = new Hangman();或调用初始化值的功能，resultstring这是hangman.initialComponent()

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编辑于 2020-09-1

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