我的代码中的Java错误线程“AWT-EventQueue-0”中的异常[重复]答案

【问题标题】：Java error in my code Exception in thread "AWT-EventQueue-0" [duplicate]我的代码中的Java错误线程“AWT-EventQueue-0”中的异常[重复]
【发布时间】：2018-08-15 19:13:40
【问题描述】：

我正在构建一个学生管理器，并从 YouTube 学到了一切。现在我陷入了困境。下面给出了代码，下面也给出了错误。

这是代码：

public class RegisterStart extends JFrame {

private JPanel contentPane;
private static JTextField uid, fname, lname, sa;
private static JPasswordField pass;
private static JComboBox sq;

private static Connection Conn;
private static ResultSet Rs;
static Properties prop;
static InputStream input;

/**
 * Launch the application.
 */
public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try 
            {
                RegisterStart frame = new RegisterStart();
                frame.setVisible(true);
                Randomize();

                input = new FileInputStream("/Users/rajat/Programming/EclipseJava/Student Manager/src/config.properties");
                prop.load(input);

                DriverManager.registerDriver(new com.mysql.cj.jdbc.Driver());
                Conn = DriverManager.getConnection(prop.getProperty("database"), prop.getProperty("dbuser"), prop.getProperty("dbpassword"));
                Randomize();
            } 
            catch (Exception e) 
            {
                e.printStackTrace();
            }
        }
    });
}


public RegisterStart() {
    setResizable(false);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 600, 440);
    contentPane = new JPanel();
    contentPane.setBackground(new Color(255, 204, 153));
    contentPane.setBorder(null);
    contentPane.setLayout(new BorderLayout(0, 0));
    setContentPane(contentPane);

    JPanel panel = new JPanel();
    panel.setBorder(new EmptyBorder(20, 0, 0, 0));
    panel.setBackground(new Color(255, 204, 153));
    contentPane.add(panel, BorderLayout.NORTH);

    JLabel lblAdminRegistration = new JLabel("ADMIN REGISTRATION");
    lblAdminRegistration.setFont(new Font("Lucida Grande", Font.PLAIN, 20));
    lblAdminRegistration.setBackground(new Color(255, 204, 153));
    panel.add(lblAdminRegistration);

    JPanel panel_1 = new JPanel();
    panel_1.setBackground(new Color(255, 204, 153));
    contentPane.add(panel_1, BorderLayout.CENTER);
    panel_1.setLayout(null);

    JLabel lblNewLabel = new JLabel("USER ID                          :");
    lblNewLabel.setBounds(62, 45, 180, 16);
    panel_1.add(lblNewLabel);

    JLabel lblNewLabel_1 = new JLabel("FIRST NAME                    :");
    lblNewLabel_1.setBounds(62, 83, 180, 16);
    panel_1.add(lblNewLabel_1);

    JLabel lblNewLabel_2 = new JLabel("LAST NAME                     :");
    lblNewLabel_2.setBounds(62, 122, 180, 16);
    panel_1.add(lblNewLabel_2);

    JLabel lblPassworf = new JLabel("PASSWORD                      :");
    lblPassworf.setBounds(62, 164, 180, 16);
    panel_1.add(lblPassworf);

    JLabel lblSecurityQuestions = new JLabel("SECURITY QUESTION        :  ");
    lblSecurityQuestions.setBounds(62, 207, 180, 16);
    panel_1.add(lblSecurityQuestions);

    uid = new JTextField();
    uid.setHorizontalAlignment(SwingConstants.CENTER);
    uid.setBackground(Color.WHITE);
    uid.setEditable(false);
    uid.setBounds(249, 40, 278, 26);
    panel_1.add(uid);
    uid.setColumns(10);

    fname = new JTextField();
    fname.setBounds(249, 78, 278, 26);
    panel_1.add(fname);
    fname.setColumns(10);

    lname = new JTextField();
    lname.setBounds(249, 117, 278, 26);
    panel_1.add(lname);
    lname.setColumns(10);

    sa = new JTextField();
    sa.setBounds(249, 246, 278, 26);
    panel_1.add(sa);
    sa.setColumns(10);

    JLabel lblSecurityAnswer = new JLabel("SECURITY ANSWER            :  ");
    lblSecurityAnswer.setBounds(62, 251, 180, 16);
    panel_1.add(lblSecurityAnswer);

    sq = new JComboBox();
    sq.setModel(new DefaultComboBoxModel(new String[] {"Which is your favorite animal?", "Who is your favorite Actor or Actress?", "Who is your first childhood friend?", "What is your hobby?", "Which is your dream Bike/Car?"}));
    sq.setBounds(249, 203, 283, 27);
    panel_1.add(sq);

    JButton regbutt = new JButton("REGISTER");
    regbutt.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            Register();
        }
    });
    regbutt.setBounds(257, 300, 117, 29);
    panel_1.add(regbutt);

    pass = new JPasswordField();
    pass.setBounds(254, 159, 273, 26);
    panel_1.add(pass);
}

private static void Randomize ()
{
    Random r = new Random (); 
    int a =  r.nextInt(1000000+1);
    uid.setText(a+"");  
}

private static void Register ()
{
    char[] pswrd = pass.getPassword();
    String pass2 = String.valueOf(pswrd);
    Calendar cal1 = new GregorianCalendar();

    java.util.Date CurrDate = cal1.getTime();
    cal1.setTime(CurrDate);
    cal1.add(Calendar.MONTH, 1);

    java.sql.Date SqlDate3 = new java.sql.Date(CurrDate.getTime());
    SimpleDateFormat DMY = new SimpleDateFormat("yyyy-mm-dd");
    DMY.format(SqlDate3);

    try 
    {
        int x=0;
        System.out.println(x++);
        PreparedStatement ps = Conn.prepareStatement("insert into admin_database values (?,?,?,?,?,?,?)");
        System.out.println(x++);
        ps.setInt(1, Integer.parseInt(uid.getText()));
        System.out.println(x++);
        ps.setString(2, fname.getText());
        System.out.println(x++);
        ps.setString(3, lname.getText());
        System.out.println(x++);
        ps.setString(4, pswrd.toString());
        System.out.println(x++);
        ps.setString(5, sq.getSelectedItem().toString());
        System.out.println(x++);
        ps.setString(6, sa.getText());
        System.out.println(x++);
        ps.setDate(7, SqlDate3);
        System.out.println(x++);

        int i = ps.executeUpdate();
        JOptionPane.showMessageDialog(null, "Thanks for Registering your UserID is "+uid.getText());
    } 
    catch (SQLException e) 
    {
        e.printStackTrace();
    }
}
}

这是我得到的错误：

java.lang.NullPointerException 在 frames.RegisterStart$1.run(RegisterStart.java:58) 在 java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313) 在 java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:770) 在 java.desktop/java.awt.EventQueue.access$600(EventQueue.java:97) 在 java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721) 在 java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715) 在 java.base/java.security.AccessController.doPrivileged（本机方法）在 java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87) 在 java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:740) 在 java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203) 在 java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124) 在 java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113) 在 java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109) 在 java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) 在 java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90) 0线程“AWT-EventQueue-0”中的异常 java.lang.NullPointerException 在 frames.RegisterStart.Register(RegisterStart.java:190) 在 frames.RegisterStart.access$2(RegisterStart.java:171) 在 frames.RegisterStart$2.actionPerformed(RegisterStart.java:153) 在 java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967) 在 java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308) 在 java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405) 在 java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262) 在 java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:270) 在 java.desktop/java.awt.Component.processMouseEvent(Component.java:6589) 在 java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342) 在 java.desktop/java.awt.Component.processEvent(Component.java:6354) 在 java.desktop/java.awt.Container.processEvent(Container.java:2261) 在 java.desktop/java.awt.Component.dispatchEventImpl(Component.java:4966) 在 java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2319) 在 java.desktop/java.awt.Component.dispatchEvent(Component.java:4798) 在 java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4914) 在 java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4543) 在 java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4484) 在 java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2305) 在 java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2772) 在 java.desktop/java.awt.Component.dispatchEvent(Component.java:4798) 在 java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772) 在 java.desktop/java.awt.EventQueue.access$600(EventQueue.java:97) 在 java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721) 在 java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715) 在 java.base/java.security.AccessController.doPrivileged（本机方法）在 java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87) 在 java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:97) 在 java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745) 在 java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743) 在 java.base/java.security.AccessController.doPrivileged（本机方法）在 java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87) 在 java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742) 在 java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203) 在 java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124) 在 java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113) 在 java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109) 在 java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) 在 java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90) 2018-08-15 22:28:31.367 java[699:58449] 查找：未处理的异常 'JavaNativeException' 在 +[LULookupDefinitionModule 中捕获 _focusTermUsingQueue:handler:]

【问题讨论】：

欢迎来到 StackOverflow。在您的答案中发布代码之前，请确保它是重现您的错误所需的最少代码量。这在 StackOverflow 上被称为 Minimal-Complete-Verifiable 示例。有关更多信息，请参见此处-stackoverflow.com/help/mcve
java.lang.NullPointerException at frames.RegisterStart$1.run(RegisterStart.java:58) - 跟踪告诉你第 58 行是问题所在。我们无能为力，因为我们不知道第 58 行是什么。找到第 58 行并确定该行上的变量为空，然后修复问题。真正的问题是你为什么要在做任何测试之前写这么多代码？？？为您的 GUI 编写几行代码并测试组件是否正确显示。然后为 SQL 添加额外的逻辑并对其进行测试。当它停止工作时，您就会知道您刚刚更改了什么，并且更容易解决问题。
您还有许多其他基本的 Swing 问题，您应该从头开始。但首先要阅读 Swing 基础知识的 [Swing 教程]()。一些提示：1）您不应该在组件上使用 setBounds() 。您应该使用布局管理器。 2）您不应该使用“静态”变量和方法。 3) 方法名称不应以大写字符开头。本教程包含您可以下载和测试的工作代码。然后更改工作代码以显示您的组件。
如果没有源代码的行号，就很难跟踪堆栈跟踪。您可以完整提交您的 RegisterStart.java 文件吗？

标签： java swing nullpointerexception awt-eventqueue

【解决方案1】：

我解决了我的问题。我刚刚将Properties prop; 更改为Properties prop = new Properties(); 这是它的样子

    public class RegisterStart extends JFrame {

    private JPanel contentPane;
    private static JTextField uid, fname, lname, sa;
    private static JPasswordField pass;
    private static JComboBox sq;

    private static Connection Conn;
    private static ResultSet Rs;
    static Properties prop = new Properties();
    static InputStream input = null;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try 
                {
                    RegisterStart frame = new RegisterStart();
                    frame.setVisible(true);
                    Randomize();

                    input = new FileInputStream("/Users/rajat/Programming/EclipseJava/Student Manager/src/config.properties");
                    prop.load(input);

                    DriverManager.registerDriver(new com.mysql.cj.jdbc.Driver());
                    Conn = DriverManager.getConnection(prop.getProperty("database"), prop.getProperty("dbuser"), prop.getProperty("dbpassword"));
                    Randomize();
                } 
                catch (Exception e) 
                {
                    e.printStackTrace();
                }
            }
        });
    }


    public RegisterStart() {
        setResizable(false);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 600, 440);
        contentPane = new JPanel();
        contentPane.setBackground(new Color(255, 204, 153));
        contentPane.setBorder(null);
        contentPane.setLayout(new BorderLayout(0, 0));
        setContentPane(contentPane);

        JPanel panel = new JPanel();
        panel.setBorder(new EmptyBorder(20, 0, 0, 0));
        panel.setBackground(new Color(255, 204, 153));
        contentPane.add(panel, BorderLayout.NORTH);

        JLabel lblAdminRegistration = new JLabel("ADMIN REGISTRATION");
        lblAdminRegistration.setFont(new Font("Lucida Grande", Font.PLAIN, 20));
        lblAdminRegistration.setBackground(new Color(255, 204, 153));
        panel.add(lblAdminRegistration);

        JPanel panel_1 = new JPanel();
        panel_1.setBackground(new Color(255, 204, 153));
        contentPane.add(panel_1, BorderLayout.CENTER);
        panel_1.setLayout(null);

        JLabel lblNewLabel = new JLabel("USER ID                          :");
        lblNewLabel.setBounds(62, 45, 180, 16);
        panel_1.add(lblNewLabel);

        JLabel lblNewLabel_1 = new JLabel("FIRST NAME                    :");
        lblNewLabel_1.setBounds(62, 83, 180, 16);
        panel_1.add(lblNewLabel_1);

        JLabel lblNewLabel_2 = new JLabel("LAST NAME                     :");
        lblNewLabel_2.setBounds(62, 122, 180, 16);
        panel_1.add(lblNewLabel_2);

        JLabel lblPassworf = new JLabel("PASSWORD                      :");
        lblPassworf.setBounds(62, 164, 180, 16);
        panel_1.add(lblPassworf);

        JLabel lblSecurityQuestions = new JLabel("SECURITY QUESTION        :  ");
        lblSecurityQuestions.setBounds(62, 207, 180, 16);
        panel_1.add(lblSecurityQuestions);

        uid = new JTextField();
        uid.setHorizontalAlignment(SwingConstants.CENTER);
        uid.setBackground(Color.WHITE);
        uid.setEditable(false);
        uid.setBounds(249, 40, 278, 26);
        panel_1.add(uid);
        uid.setColumns(10);

        fname = new JTextField();
        fname.setBounds(249, 78, 278, 26);
        panel_1.add(fname);
        fname.setColumns(10);

        lname = new JTextField();
        lname.setBounds(249, 117, 278, 26);
        panel_1.add(lname);
        lname.setColumns(10);

        sa = new JTextField();
        sa.setBounds(249, 246, 278, 26);
        panel_1.add(sa);
        sa.setColumns(10);

        JLabel lblSecurityAnswer = new JLabel("SECURITY ANSWER            :  ");
        lblSecurityAnswer.setBounds(62, 251, 180, 16);
        panel_1.add(lblSecurityAnswer);

        sq = new JComboBox();
        sq.setModel(new DefaultComboBoxModel(new String[] {"Which is your favorite animal?", "Who is your favorite Actor or Actress?", "Who is your first childhood friend?", "What is your hobby?", "Which is your dream Bike/Car?"}));
        sq.setBounds(249, 203, 283, 27);
        panel_1.add(sq);

        JButton regbutt = new JButton("REGISTER");
        regbutt.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                Register();
            }
        });
        regbutt.setBounds(257, 300, 117, 29);
        panel_1.add(regbutt);

        pass = new JPasswordField();
        pass.setBounds(254, 159, 273, 26);
        panel_1.add(pass);
    }

    private static void Randomize ()
    {
        Random r = new Random (); 
        int a =  r.nextInt(1000000+1);
        uid.setText(a+"");  
    }

    private static void Register ()
    {
        char[] pswrd = pass.getPassword();
        String pass2 = String.valueOf(pswrd);
        Calendar cal1 = new GregorianCalendar();

        java.util.Date CurrDate = cal1.getTime();
        cal1.setTime(CurrDate);
        cal1.add(Calendar.MONTH, 1);

        java.sql.Date SqlDate3 = new java.sql.Date(CurrDate.getTime());
        SimpleDateFormat DMY = new SimpleDateFormat("yyyy-mm-dd");
        DMY.format(SqlDate3);

        try 
        {
            PreparedStatement ps = Conn.prepareStatement("insert into admin_database values (?,?,?,?,?,?,?)");
            ps.setInt(1, Integer.parseInt(uid.getText()));
            ps.setString(2, fname.getText());
            ps.setString(3, lname.getText());
            ps.setString(4, pswrd.toString());
            ps.setString(5, sq.getSelectedItem().toString());
            ps.setString(6, sa.getText());
            ps.setDate(7, SqlDate3);

            int i = ps.executeUpdate();
            JOptionPane.showMessageDialog(null, "Thanks for Registering your UserID is "+uid.getText());
        } 
        catch (SQLException e) 
        {
            e.printStackTrace();
        }
    }
}

【讨论】：