I want to add update button to GroupLayout but program throwing illegal argument Exception

Question

I want to add update button to GroupLayout but program throwing illegal argument Exception:

public class UsingFile extends javax.swing.JFrame {
 DefaultTableModel dtm;

    public UsingFile()
    {
        initComponents();`exception at this point`

        dtm = (DefaultTableModel)myjtable.getModel();
        readFile();
    }

  private void initComponents()  
{

        jPanel1 = new javax.swing.JPanel();
        jLabel1 = new javax.swing.JLabel();
        jScrollPane1 = new javax.swing.JScrollPane();
        myjtable = new javax.swing.JTable();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        jLabel5 = new javax.swing.JLabel();
        txtitem = new javax.swing.JTextField();
        txtprice = new javax.swing.JTextField();
        txtquantity=new javax.swing.JTextField();
        txtreorder=new javax.swing.JTextField();
        btnadd = new javax.swing.JButton();
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jLabel1)
                .addContainerGap(80, Short.MAX_VALUE)));
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                .addContainerGap(21, Short.MAX_VALUE)
                .addComponent(jLabel1)
                .addContainerGap()) );

        myjtable.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {

            },
            new String [] {
                "Item", "Price","quantity","reorder"
            }
        ));
        jScrollPane1.setViewportView(myjtable);

        jLabel2.setText("Item");

        jLabel3.setText("Price");

        jLabel4.setText("quantity");

        jLabel5.setText("reorder");

        btnadd.setText("Add");
        btnadd.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnaddActionPerformed(evt);
            }
        }
     );


        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addGroup(layout.createSequentialGroup()
                        .addContainerGap()
                        .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 421, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addGroup(layout.createSequentialGroup()
                        .addGap(19, 19, 19)
                        .addComponent(jLabel2)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(txtitem, javax.swing.GroupLayout.PREFERRED_SIZE, 166, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(jLabel3)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(txtprice, javax.swing.GroupLayout.DEFAULT_SIZE, 114, Short.MAX_VALUE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(jLabel4)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(txtquantity, javax.swing.GroupLayout.DEFAULT_SIZE, 114, Short.MAX_VALUE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)

                        .addComponent(jLabel5)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(txtreorder, javax.swing.GroupLayout.DEFAULT_SIZE, 114, Short.MAX_VALUE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)

                        .addComponent(btnadd)))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(btnupdate)));`here i am adding Update button`


        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2)
                    .addComponent(txtitem, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel3)
                    .addComponent(txtprice, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel4)
                    .addComponent(txtquantity, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel5)
                    .addComponent(txtreorder, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(btnadd))
                   .addComponent(btnupdate)
                    .addComponent(btnupdate)

                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 129, Short.MAX_VALUE)
                .addContainerGap())
        );

        pack();


    }



    private void btnaddActionPerformed(java.awt.event.ActionEvent evt) 
    {
       String item = txtitem.getText();
       String price = txtprice.getText();
       String quantity=txtquantity.getText();
       String reorder=txtreorder.getText();


       try {


           String filename= "MyFile.txt";


                FileWriter myfile = new FileWriter(filename,true);

                PrintWriter outStream = new PrintWriter(myfile);
                    outStream.print(item);
                    outStream.print("|");
                    outStream.print(price);
                    outStream.print("|");
                    outStream.print(quantity);
                    outStream.print("|");
                    outStream.print(reorder);
                    outStream.print("\r\n");
                    outStream.close();

                    txtitem.setText("");
                    txtprice.setText("");
                    txtquantity.setText("");
                    txtreorder.setText("");


                    readFile();
       } catch (Exception e) {
                e.printStackTrace();}


     }//end of button action 



    private void readFile()
    {
        BufferedReader br = null;

        try {

            String sCurrentLine;

            br = new BufferedReader(new FileReader("C:\\uttara\\workspace\\FileDemo\\MyFile.txt"));

            if (dtm.getRowCount() > 0) {
                for (int i = dtm.getRowCount() - 1; i > -1; i--) {
                    dtm.removeRow(i);
                }
            }
            while ((sCurrentLine = br.readLine()) != null) {

                String item1=sCurrentLine.toString();

                String regexp = "[|]+";

                String[] lines = item1.split(regexp);

             Vector v = new Vector();           

                   String item2;
                   String price2;
                   String quantity2;
                   String reorder2;

                   item2=lines[0].toString();
                   price2=lines[1].toString();
                   quantity2=lines[2].toString();
                   reorder2=lines[3].toString();


                   v.add(item2);
                   v.add(price2);
                   v.add(quantity2);
                   v.add(reorder2);

                   dtm.toString();
                   dtm.addRow(v); 


    }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (br != null)br.close();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }




    public static void main(String args[]) {


        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new UsingFile().setVisible(true); `error at this point`

            }
        });
    }


    'here i am initializing the components'

    private javax.swing.JButton btnadd;
    private javax.swing.JButton btnupdate;

    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.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTable myjtable;

    private javax.swing.JTextField txtitem;
    private javax.swing.JTextField txtprice;
    private javax.swing.JTextField txtquantity;
    private javax.swing.JTextField txtreorder;

}

Answer 1

at the point that you are adding the button it is null (so it's not a button) if you just change the declaration of it to something like this:

private javax.swing.JButton btnupdate = new JButton();

you will get further along....