JFrame - help

what an earth have I done wrong here - I WAS sure that I was on the right track. This code compiles then error:

Code:

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import java.io.*;
        import java.awt.*;
        import java.awt.event.*;
        import javax.swing.*;

        class ExampleFrame2a extends JFrame implements WindowListener {

        public static void main (String [] args) {
               
        ExampleFrame2a demo = new ExampleFrame2a();  // create an instance of the ExampleFrame object
               
                demo.setLayout(new GridLayout(4,4));  // set Layout manager to Grid Layout
        demo.setSize(900,700);
        demo.addWindowListener(demo);  // register listener for window events, eg close
               
                String s=readTextFile("poem.txt"); // read from the poem file to a String
               
                Label fnameL = new Label("First Name");
                demo.add(fnameL);
                TextField fnameTF = new TextField(10);
                demo.add(fnameTF);

                Label SnameL = new Label("Surname");
                demo.add(SnameL);
                TextField SnameTF = new TextField(10);
                demo.add(SnameTF);
               
                Label StreetL = new Label("Street");
                demo.add(StreetL);
                TextField StreetTF = new TextField(10);
                demo.add(StreetTF);
               
                Label CityL = new Label("City");
                demo.add(CityL);
                TextField CityTF = new TextField(10);
                demo.add(CityTF);

                Label CountyL = new Label("County");
                demo.add(CountyL);
                TextField CountyTF = new TextField(10);
                demo.add(CountyTF);

                Label PCodeL = new Label("Post Code");
                demo.add(PCodeL);
                TextField PCodeTF = new TextField(10);
                demo.add(PCodeTF);

                TextArea myTextArea = new TextArea("",10,50);  // create a text area and add  it to the frame
                demo.add(myTextArea);
               
                myTextArea.append(s); // append text from file to the text area
       
                demo.setVisible(true);        // make Frame visible
   
                }

        public static String readTextFile(String filename) {
       
                BufferedReader inFile;
                String line, s = "";  // intialize s
       
                try

                {
                        inFile = new BufferedReader(new FileReader(filename));

                while ( (line = inFile.readLine()) != null )
                {
                        s = s + line + "\n"; // concatenate onto s, WITH  // AN EXTRA NEW LINE
 
                }
                        inFile.close();
                }
                catch (IOException e)
                {
                System.out.println("Error in file " + filename + " : "        +  e.toString() );
                System.exit(1);  // better if -1, means standard error
                }
       
                return s;
                }
       
    public void windowClosing(WindowEvent e) {  // code to handle closing the window
        System.exit(0);
            }
   
                //unused empty WindowListener Methods --- needed to enable a                // compile
                public void windowIconified(WindowEvent e) {
                }
                public void windowOpened(WindowEvent e) {
                }
                public void windowClosed(WindowEvent e) {
                }
                public void windowDeiconified(WindowEvent e) {
                }
                public void windowActivated(WindowEvent e) {
                }
                public void windowDeactivated(WindowEvent e) {
                }
        }

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The root components JFrame, JWindow, JDialog, JApplet and the lightweight container JInternalFrame() use the containment model provided by the root pane class. What this means is you must work with the content pane rather than the top level object itself. Since your ExampleFrame2a class extends JFrame the layout manager must be set on the content pane not the JFrame. Same goes for adding components to a top level object. They must be added to the content pane. There are multiple ways to do this.

Code:

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JFrame jf = new JFrame();
JLabel jl = new JLabel();
Container c  = jf.getContentPane();
c.add(jl);

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Code:

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JFrame jf = new JFrame();
jf.getContentPane().add(new JLabel());

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The content pane can be obtained by first retrieving the root pane component then extracting the content pane, which is located inside the layered pane. But this can be very akward.

Code:

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JRootPane rp  = jf.getRootPane();
JLayeredPane jlp = rp.getLayeredPane();

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