When I press the "show" button it does not show any table and error

In summary, the conversation is about debugging code and the importance of learning how to do it. The speaker asks what tools are being used for debugging and suggests using a debugger or adding print statements to track the code's progress.
  • #1
Suxil_7
1
0
I need help. When I press show button it does not show any table and error.
Here is the code:
Java:
package Demo;

import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.table.DefaultTableModel;
import javax.swing.JTable;
import javax.swing.JScrollPane;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.awt.event.ActionEvent;

@SuppressWarnings("serial")
public class Datatable extends JFrame {

    private JPanel contentPane;
    private JTable table;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Datatable frame = new Datatable();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public Datatable() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 450, 300);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));

        setContentPane(contentPane);
        contentPane.setLayout(null);
      
        JScrollPane scrollPane = new JScrollPane();
        scrollPane.setBounds(235, 172, -177, -125);
        contentPane.add(scrollPane);
      
        table = new JTable();
        scrollPane.setViewportView(table);
      
        JButton btnNewButton = new JButton("Show");
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                try {
                    Class.forName("com.mysql.cj.jdbc.Driver");
                    Connection con =DriverManager.getConnection("jdbc:mysql://localhost:3306/mybd","root","");
                    Statement st = con.createStatement();
                    String query = "Select * from student";
                    ResultSet rs =st.executeQuery(query);
                    ResultSetMetaData rsmd=rs.getMetaData();
                    DefaultTableModel model =(DefaultTableModel)table.getModel();
                    int cols =rsmd.getColumnCount();
                    String [] colName = new String[cols];
                    for(int i =0; i<cols;i++) {
                        colName[ i] =rsmd.getColumnName(i+1);
                        model.setColumnIdentifiers(colName);
                        String id,name,course;
                        while(rs.next()) {
                            id= rs.getString(1);
                            name= rs.getString(2);
                            course= rs.getString(3);
                           
                            String[] row = {id,name,course};
                            model.addRow(row);
                        }
                    //    rs.close();
                        //st.close();
                //con.close();
                       
                    }
                } catch (ClassNotFoundException | SQLException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
           
            }
        });
        btnNewButton.setBounds(326, 69, 85, 21);
        contentPane.add(btnNewButton);
    }
}
 
Last edited by a moderator:
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  • #2
One of the most important things to learn in programming anything is how to debug your code. What are you using to debug? Are you running it in a debugger where you can step through the code? Have you tried to place prints or display messages at key locations to see what is happening?
 
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