So, I have a method that (should) return a String containing a data from a sqlite database:
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);
}
and I would use that string to locate a text file by which its content will be displayed on a JTextPane that is located from another class
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);
}
}
however I am getting this error:
Exception in thread "AWT-EventQueue-0" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 at java.util.ArrayList.rangeCheck(ArrayList.java:657) at java.util.ArrayList.get(ArrayList.java:433) at mainWindow.openLesson.getLesson(openLesson.java:204) at mainWindow.openLesson.btnOpenLessonPopUpActionPerformed(openLesson.java:126) at mainWindow.openLesson.access$000(openLesson.java:19) at 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.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:6539) at javax.swing.JComponent.processMouseEvent(JComponent.java:3324) at java.awt.Component.processEvent(Component.java:6304) at java.awt.Container.processEvent(Container.java:2239) at java.awt.Component.dispatchEventImpl(Component.java:4889) at java.awt.Container.dispatchEventImpl(Container.java:2297) at java.awt.Component.dispatchEvent(Component.java:4711) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4904) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4535) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4476) at java.awt.Container.dispatchEventImpl(Container.java:2283) at java.awt.Window.dispatchEventImpl(Window.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) at java.awt.EventQueue$3.run(EventQueue.java:709) at java.awt.EventQueue$3.run(EventQueue.java:703) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:84) at java.awt.EventQueue$4.run(EventQueue.java:733) at java.awt.EventQueue$4.run(EventQueue.java:731) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74) at java.awt.EventQueue.dispatchEvent(EventQueue.java:730) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93) at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
I don't think I have any idea of why this is happening. I'm still new to programming.
Difficult to say without knowing the structure of your data, however, from your query: "SELECT * FROM lessons WHERE lesson_id = '" + name + "';" it seems that you are trying to match the lesson_id with the name of the lesson your are getting.
It could also be that String name = (String) tblOpenLesson.getModel().getValueAt(selectedRow, selectedColumn); doesn't give you what you'd expect.
On another note, you really need to look into Prepared Statements. As is, your application is prone to SQL injection.
Personally, I would also refactor the code so that:
if (rs.next()) {
list.add(rs.getString("lesson"));
}
Becomes:
if (rs.next()) {
return rs.getString("lesson");
}
And this: return (String) list.get(0); becomes return "";.