空指针异常java代码

我试图在netbeans中创建一个电子邮件客户端来发送电子邮件，但我的代码中出现了空指针异常。这是我的代码（有三个类）：

EmailClient.java

package sendemail;

public class EmailClient extends javax.swing.JFrame {

    SendMail sm=new SendMail();
    Settings set=new Settings();
    public EmailClient() {
        initComponents();
    }


    @SuppressWarnings("unchecked")
    +Generated code                     

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
       // TODO add your handling code here:
        sm.setVisible(true);
    }                                        

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jMenuItem2ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        // TODO add your handling code here:
        set.setVisible(true);
    }                                          

    public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new EmailClient().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JButton jButton3;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel jLabel5;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JMenu jMenu4;
    private javax.swing.JMenu jMenu5;
    private javax.swing.JMenuBar jMenuBar2;
    private javax.swing.JMenuItem jMenuItem2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel3;
    private javax.swing.JPanel jPanel4;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    // End of variables declaration                   


}

package sendemail;
import javax.swing.*;
import java.awt.*;

public class Settings extends javax.swing.JFrame {

    public String uname;
    public String pass;
    public String smtpserver;
    public String  port;
    /**
     * Creates new form Settings
     */
    public Settings() {
        initComponents();
    }

    public String getUname() {
        return uname;
    }

    public String getPass() {
        return pass;
    }

    public String getSmtpserver() {
        return smtpserver;
    }

    public String getPort() {
        return port;
    }



    @SuppressWarnings("unchecked")
    +Generated Code                   

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
       uname=jTextField1.getText().toString();
        pass=jPasswordField1.getPassword().toString();

        smtpserver=jComboBox1.getSelectedItem().toString();
        port=jComboBox2.getSelectedItem().toString();

        if(uname.equals("") || pass.equals("") || smtpserver.equals("") || port.equals("") )
    {
            JOptionPane.showMessageDialog(this,"All Fields are mandatory");
    }                                        
    else
        {
            setVisible(false);
        }

    }                                        

    private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        // TODO add your handling code here:
    }                                          

    public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Settings().setVisible(false);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JComboBox jComboBox1;
    private javax.swing.JComboBox jComboBox2;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPasswordField jPasswordField1;
    private javax.swing.JTextField jTextField1;
    // End of variables declaration                   
    jTextField1=new JTextField();
}

package sendemail;

import java.util.Properties;
import javax.mail.Message;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.swing.JOptionPane;
import java.awt.*;
import javax.mail.*;
import javax.mail.MessagingException;


public class SendMail extends javax.swing.JFrame {

    Settings setfrm=new Settings();
    String subject;
    String from;

    public SendMail() {
        initComponents();
    }


    @SuppressWarnings("unchecked")
    +Generated Code                    

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
        try
        {
        final String user=setfrm.getUname();
        final String password=setfrm.getPass();
        String portnum=setfrm.getPort();
        String smtpname=setfrm.getSmtpserver();
        String to=jTextField1.getText();
        subject=jTextField2.getText();
        Properties properties=new Properties();
        properties.put("mail.smtp.host",smtpname.toString());
        properties.put("mail.smtp.socketFactory.port",portnum.toString());
        properties.put("mail.smtp.socketFactory.class","javax.net.ssl.SSLSocketFactory");
        properties.put("mail.smtp.port",portnum.toString());
        properties.put("mail.smtp.auth","true");
        Session session=Session.getDefaultInstance(properties,
           new javax.mail.Authenticator() {
               protected PasswordAuthentication getPasswordAuthentication(){
                return new PasswordAuthentication(user,password);

           }

           }

           );
        MimeMessage message=new MimeMessage(session);
        message.setFrom(new InternetAddress(user));
        message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(jTextField1.getText().toString()));
        message.setSubject(subject);
        message.setText(jTextArea1.getText());
        Transport.send(message);
        JOptionPane.showMessageDialog(null,"message sent");
        }
        catch(MessagingException mex)
        {
            JOptionPane.showMessageDialog(null,mex);
        }
    }                                        

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jTextField1ActionPerformed(java.awt.event.ActionEvent evt) {                                            
        // TODO add your handling code here:
    }                                           

    public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new SendMail().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JTextField jTextField2;
    // End of variables declaration                   
    jTextField1=new JTextField();
    jTextField2=new JTextField();
}

Settings.java

package sendemail;

public class EmailClient extends javax.swing.JFrame {

    SendMail sm=new SendMail();
    Settings set=new Settings();
    public EmailClient() {
        initComponents();
    }


    @SuppressWarnings("unchecked")
    +Generated code                     

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
       // TODO add your handling code here:
        sm.setVisible(true);
    }                                        

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jMenuItem2ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        // TODO add your handling code here:
        set.setVisible(true);
    }                                          

    public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new EmailClient().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JButton jButton3;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel jLabel5;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JMenu jMenu4;
    private javax.swing.JMenu jMenu5;
    private javax.swing.JMenuBar jMenuBar2;
    private javax.swing.JMenuItem jMenuItem2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel3;
    private javax.swing.JPanel jPanel4;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    // End of variables declaration                   


}

package sendemail;
import javax.swing.*;
import java.awt.*;

public class Settings extends javax.swing.JFrame {

    public String uname;
    public String pass;
    public String smtpserver;
    public String  port;
    /**
     * Creates new form Settings
     */
    public Settings() {
        initComponents();
    }

    public String getUname() {
        return uname;
    }

    public String getPass() {
        return pass;
    }

    public String getSmtpserver() {
        return smtpserver;
    }

    public String getPort() {
        return port;
    }



    @SuppressWarnings("unchecked")
    +Generated Code                   

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
       uname=jTextField1.getText().toString();
        pass=jPasswordField1.getPassword().toString();

        smtpserver=jComboBox1.getSelectedItem().toString();
        port=jComboBox2.getSelectedItem().toString();

        if(uname.equals("") || pass.equals("") || smtpserver.equals("") || port.equals("") )
    {
            JOptionPane.showMessageDialog(this,"All Fields are mandatory");
    }                                        
    else
        {
            setVisible(false);
        }

    }                                        

    private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        // TODO add your handling code here:
    }                                          

    public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Settings().setVisible(false);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JComboBox jComboBox1;
    private javax.swing.JComboBox jComboBox2;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPasswordField jPasswordField1;
    private javax.swing.JTextField jTextField1;
    // End of variables declaration                   
    jTextField1=new JTextField();
}

package sendemail;

import java.util.Properties;
import javax.mail.Message;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.swing.JOptionPane;
import java.awt.*;
import javax.mail.*;
import javax.mail.MessagingException;


public class SendMail extends javax.swing.JFrame {

    Settings setfrm=new Settings();
    String subject;
    String from;

    public SendMail() {
        initComponents();
    }


    @SuppressWarnings("unchecked")
    +Generated Code                    

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
        try
        {
        final String user=setfrm.getUname();
        final String password=setfrm.getPass();
        String portnum=setfrm.getPort();
        String smtpname=setfrm.getSmtpserver();
        String to=jTextField1.getText();
        subject=jTextField2.getText();
        Properties properties=new Properties();
        properties.put("mail.smtp.host",smtpname.toString());
        properties.put("mail.smtp.socketFactory.port",portnum.toString());
        properties.put("mail.smtp.socketFactory.class","javax.net.ssl.SSLSocketFactory");
        properties.put("mail.smtp.port",portnum.toString());
        properties.put("mail.smtp.auth","true");
        Session session=Session.getDefaultInstance(properties,
           new javax.mail.Authenticator() {
               protected PasswordAuthentication getPasswordAuthentication(){
                return new PasswordAuthentication(user,password);

           }

           }

           );
        MimeMessage message=new MimeMessage(session);
        message.setFrom(new InternetAddress(user));
        message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(jTextField1.getText().toString()));
        message.setSubject(subject);
        message.setText(jTextArea1.getText());
        Transport.send(message);
        JOptionPane.showMessageDialog(null,"message sent");
        }
        catch(MessagingException mex)
        {
            JOptionPane.showMessageDialog(null,mex);
        }
    }                                        

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jTextField1ActionPerformed(java.awt.event.ActionEvent evt) {                                            
        // TODO add your handling code here:
    }                                           

    public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new SendMail().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JTextField jTextField2;
    // End of variables declaration                   
    jTextField1=new JTextField();
    jTextField2=new JTextField();
}

SendMail.Java

package sendemail;

public class EmailClient extends javax.swing.JFrame {

    SendMail sm=new SendMail();
    Settings set=new Settings();
    public EmailClient() {
        initComponents();
    }


    @SuppressWarnings("unchecked")
    +Generated code                     

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
       // TODO add your handling code here:
        sm.setVisible(true);
    }                                        

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jMenuItem2ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        // TODO add your handling code here:
        set.setVisible(true);
    }                                          

    public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new EmailClient().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JButton jButton3;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel jLabel5;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JMenu jMenu4;
    private javax.swing.JMenu jMenu5;
    private javax.swing.JMenuBar jMenuBar2;
    private javax.swing.JMenuItem jMenuItem2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel3;
    private javax.swing.JPanel jPanel4;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    // End of variables declaration                   


}

package sendemail;
import javax.swing.*;
import java.awt.*;

public class Settings extends javax.swing.JFrame {

    public String uname;
    public String pass;
    public String smtpserver;
    public String  port;
    /**
     * Creates new form Settings
     */
    public Settings() {
        initComponents();
    }

    public String getUname() {
        return uname;
    }

    public String getPass() {
        return pass;
    }

    public String getSmtpserver() {
        return smtpserver;
    }

    public String getPort() {
        return port;
    }



    @SuppressWarnings("unchecked")
    +Generated Code                   

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
       uname=jTextField1.getText().toString();
        pass=jPasswordField1.getPassword().toString();

        smtpserver=jComboBox1.getSelectedItem().toString();
        port=jComboBox2.getSelectedItem().toString();

        if(uname.equals("") || pass.equals("") || smtpserver.equals("") || port.equals("") )
    {
            JOptionPane.showMessageDialog(this,"All Fields are mandatory");
    }                                        
    else
        {
            setVisible(false);
        }

    }                                        

    private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        // TODO add your handling code here:
    }                                          

    public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Settings().setVisible(false);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JComboBox jComboBox1;
    private javax.swing.JComboBox jComboBox2;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPasswordField jPasswordField1;
    private javax.swing.JTextField jTextField1;
    // End of variables declaration                   
    jTextField1=new JTextField();
}

package sendemail;

import java.util.Properties;
import javax.mail.Message;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.swing.JOptionPane;
import java.awt.*;
import javax.mail.*;
import javax.mail.MessagingException;


public class SendMail extends javax.swing.JFrame {

    Settings setfrm=new Settings();
    String subject;
    String from;

    public SendMail() {
        initComponents();
    }


    @SuppressWarnings("unchecked")
    +Generated Code                    

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
        try
        {
        final String user=setfrm.getUname();
        final String password=setfrm.getPass();
        String portnum=setfrm.getPort();
        String smtpname=setfrm.getSmtpserver();
        String to=jTextField1.getText();
        subject=jTextField2.getText();
        Properties properties=new Properties();
        properties.put("mail.smtp.host",smtpname.toString());
        properties.put("mail.smtp.socketFactory.port",portnum.toString());
        properties.put("mail.smtp.socketFactory.class","javax.net.ssl.SSLSocketFactory");
        properties.put("mail.smtp.port",portnum.toString());
        properties.put("mail.smtp.auth","true");
        Session session=Session.getDefaultInstance(properties,
           new javax.mail.Authenticator() {
               protected PasswordAuthentication getPasswordAuthentication(){
                return new PasswordAuthentication(user,password);

           }

           }

           );
        MimeMessage message=new MimeMessage(session);
        message.setFrom(new InternetAddress(user));
        message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(jTextField1.getText().toString()));
        message.setSubject(subject);
        message.setText(jTextArea1.getText());
        Transport.send(message);
        JOptionPane.showMessageDialog(null,"message sent");
        }
        catch(MessagingException mex)
        {
            JOptionPane.showMessageDialog(null,mex);
        }
    }                                        

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jTextField1ActionPerformed(java.awt.event.ActionEvent evt) {                                            
        // TODO add your handling code here:
    }                                           

    public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new SendMail().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JTextField jTextField2;
    // End of variables declaration                   
    jTextField1=new JTextField();
    jTextField2=new JTextField();
}

我正在尝试使用SendMail.java发送电子邮件，而发件人的电子邮件和密码是从Settings.java输入的，EmailClient.java只是用于在单击按钮时将JFrames可见性设置为true或false

错误：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at sendemail.SendMail.jButton1ActionPerformed(SendMail.java:157)
    at sendemail.SendMail.access$100(SendMail.java:24)
    at sendemail.SendMail$2.actionPerformed(SendMail.java:76)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6505)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3311)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:694)
    at java.awt.EventQueue$3.run(EventQueue.java:692)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:708)
    at java.awt.EventQueue$4.run(EventQueue.java:706)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

---

jTextField1

为空，需要像

JTextField jTextField1=新的JTextField（）

我还看到所有的成员字段都没有正确初始化。您需要确保所有实例成员字段在调用任何方法调用之前都已初始化
Stacktrace，请！哪一行生成NPE？哪一行的变量为null？如果不发布stacktrace，我们将无能为力。嘿，我正在使用Netbeans IDE编写此代码，因此初始化部分已经由Netbeans完成。您需要使用
new
关键字对其进行初始化。请不要使用太多的IDE。你不会学到太多的语言知识。我已经更新了代码，但仍然会出错…同样的错误我认为你的代码不会编译。在方法之外，不能在声明之后初始化。您必须在声明期间或在任何方法（包括构造函数）内初始化它