IndexOutOfBounds。您应该如何将结果集中的数据存储到ArrayList中？

因此，我有一个方法（应该）返回一个包含来自sqlite数据库的数据的字符串：

public String getLesson() throws ClassNotFoundException {
    ArrayList list = new ArrayList();

    int selectedColumn = tblOpenLesson.getSelectedColumn();
    int selectedRow = tblOpenLesson.getSelectedRow();
    String name = (String) tblOpenLesson.getModel().getValueAt(selectedRow, selectedColumn);

    try {
        Class.forName("org.sqlite.JDBC");
        Connection con = DriverManager.getConnection("jdbc:sqlite:sql_items.sqlite");
        Statement stmtGetLesson = con.createStatement();
        ResultSet rs = stmtGetLesson.executeQuery("SELECT * FROM lessons WHERE lesson_id  = '" + name + "';");

        if (rs.next()) {
            list.add(rs.getString("lesson"));
        }
    } catch (SQLException e) {
        JOptionPane.showMessageDialog(null, e);
    } catch (ClassNotFoundException ex) {
        Logger.getLogger(openLesson.class.getName()).log(Level.SEVERE, null, ex);
    }

    return (String) list.get(0);
}

我将使用该字符串找到一个文本文件，通过该文本文件，其内容将显示在另一个类的JTextPane上

private void btnOpenLessonPopUpActionPerformed(java.awt.event.ActionEvent evt) {                                                   

    try {
        FileReader fr = new FileReader("Lessons\\" + getLesson() + ".txt"); //this is Line 126

        try (BufferedReader br = new BufferedReader(fr)) {
            mainScreen.lessonPane.read(br, null); //  lessonPane is from another class
            br.close();
        } catch (IOException e) {
            System.out.println(e);
            this.setVisible(false);
        } catch (ClassNotFoundException ex) {
            Logger.getLogger(openLesson.class.getName()).log(Level.SEVERE, null, ex);
        }  
    } 

但是我收到此错误：

线程“ AWT-EventQueue-0”中的异常

java.lang.IndexOutOfBoundsException：Index：0，Size：0 at java.util.ArrayList.rangeCheck（ArrayList.java:657）at java.util.ArrayList.get（ArrayList.java） ：433）在mainWindow.openLesson.getLesson（openLesson.java:204）在mainWindow.openLesson.btnOpenLessonPopUpActionPerformed（openLesson.java:126）在mainWindow.openLesson.access $ 000（openLesson.java:19）在mainWindow.openLesson $ 1.actionPerformed （openLesson.java:60）at javax.swing.AbstractButton.fireActionPerformed（AbstractButton.java:2022）at javax.swing.AbstractButton $ Handler.actionPerformed（AbstractButton.java:2348）at javax.swing.DefaultButtonModel.fireActionPerformed（DefaultButtonModel。 javax：swing.plaf.basic上的javax.swing.DefaultButtonModel.setPressed（DefaultButtonModel.java:259）上的java：402）。java.awt.Component.processMouseEvent（Component.java:6539）的BasicButtonListener.mouseReleased（BasicButtonListener.java:252）在java.awt.Component.processEvent（Component）的javax.swing.JComponent.processMouseEvent（JComponent.java:3324） .java：6304），位于java.awt.Container.processEvent（Container.java：2239），位于java.awt.Component.dispatchEventImpl（Component.java：4889），位于java.awt.Container.dispatchEventImpl（Container.java：2297）在java.awt.LightweightDispatcher.processMouseEvent（Container.java:4535）在java.awt.LightweightDispatcher.retargetMouseEvent（Container.java:4904）在java.awt.LightweightDispatcher.processMouseEvent（Container.java:4535）在java.awt.Component.dispatchEvent（Component.java:4711）位于java.awt.Window.dispatchEventImpl（Window.java.awt.Container.dispatchEventImpl（Container.java:2283）的LightweightDispatcher.dispatchEvent（Container.java:4476）java：2746）at java.awt.Component.dispatchEvent（Component.java:4711）at java.awt.EventQueue.dispatchEventImpl（EventQueue.java:760）at java.awt.EventQueue.access $ 500（EventQueue.java:97）在java.awt.EventQueue $ 3.run（EventQueue.java:709）在java.awt.EventQueue $ 3.run（EventQueue.java:703）在java.security.AccessController.doPrivileged（Native Method）在java.security.ProtectionDomain java.security.ProtectionDomain $ JavaSecurityAccessImpl.doIntersectionPrivilege（ProtectionDomain.java:84）处的$ JavaSecurityAccessImpl.doIntersectionPrivilege（ProtectionDomain.java:74）在java.awt.EventQueue处java.awt.EventQueue $ 4.run（EventQueue.java:733）处java.security.ProtectionDomain $ JavaSecurityAccessImpl上的java.security.AccessController.doPrivileged（本机方法）$ 4.run（EventQueue.java:731）。doIntersectionPrivilege（ProtectionDomain.java:74）在java.awt.EventQueue.dispatchEvent（EventQueue.java:730）在java.awt.EventDispatchThread.pumpOneEventForFilters（EventDispatchThread.java:205）在java.awt.EventDispatchThread.pumpEventsForFilter（EventDispatchThread.java ：116）在java.awt.EventDispatchThread.pumpEventsForHierarchy（EventDispatchThread.java:105）在java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:101）在java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:93）在Java .awt.EventDispatchThread.run（EventDispatchThread.java:82）java.awt.EventDispatchThread.pumpEventsForHierarchy（EventDispatchThread.java:105）处PumpEventsForFilter（EventDispatchThread.java:116）在java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.pumpEvents（EventDispatchThread.java:101）处：93）at java.awt.EventDispatchThread.run（EventDispatchThread.java:82）java.awt.EventDispatchThread.pumpEventsForHierarchy（EventDispatchThread.java:105）处PumpEventsForFilter（EventDispatchThread.java:116）在java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.pumpEvents（EventDispatchThread.java:101）处：93）at java.awt.EventDispatchThread.run（EventDispatchThread.java:82）

我不知道为什么会这样。我还是编程新手。

问题来源：Stack Overflow