How to get related data of selected item from one ComboBox to another ComboBox in java

Question

I am creating a program in which I have two comboBoxes "jComboBox1" & "jComboBox2". "jComboBox1" is retrieving all the banks from the database. While "jComboBox2" should bring all the accounts of the selected bank. Now, I manage to retrieve all the banks in "jComboBox1". But I do not understand how to connect it with the second comboBox.
My code is as follows.

package frame;

import java.beans.Statement;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import javax.swing.*;
//import org.apache.pdfbox.pdmodel.*;
import java.io.*;

public class print_cheque extends javax.swing.JFrame  {
    public print_cheque() {
        initComponents();
        Connection con = null;
        //Statement st =  null;
        String query = "Select bnk_nm from d_bank_mst";
        try {
            Class.forName("oracle.jdbc.driver.OracleDriver");
            con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:ora10g", "payablek", "payablek");
            System.out.println("connection successful");

            java.sql.Statement st = con.createStatement();
            ResultSet rs = st.executeQuery(query);

            while (rs.next()) {
                String bank = rs.getString(1);
                jComboBox1.addItem(bank);
            }
            //con.close();
            st.close();
        } catch (Exception e) {
            JOptionPane.showMessageDialog(this, e);
        }

    }

    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jComboBox1 = new javax.swing.JComboBox<>();
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jComboBox2 = new javax.swing.JComboBox<>();
        jLabel3 = new javax.swing.JLabel();
        jComboBox3 = new javax.swing.JComboBox<>();
        jLabel4 = new javax.swing.JLabel();
        jComboBox4 = new javax.swing.JComboBox<>();
        jRadioButton1 = new javax.swing.JRadioButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jComboBox1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jComboBox1ActionPerformed(evt);
            }
        });

        jLabel1.setText("Bank Name");

        jLabel2.setText("Account No");

        jComboBox2.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));

        jLabel3.setText("From Cheque No");

        jComboBox3.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));

        jLabel4.setText("To Cheque No");

        jComboBox4.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));

        jRadioButton1.setText("Cash");
        jRadioButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jRadioButton1ActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(33, 33, 33)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                            .addComponent(jLabel2)
                            .addComponent(jLabel1)))
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                        .addContainerGap()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jLabel3, javax.swing.GroupLayout.Alignment.TRAILING)
                            .addComponent(jLabel4, javax.swing.GroupLayout.Alignment.TRAILING))))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                        .addComponent(jComboBox2, 0, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(jComboBox1, 0, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(jComboBox3, 0, 253, Short.MAX_VALUE)
                        .addComponent(jComboBox4, 0, 253, Short.MAX_VALUE))
                    .addComponent(jRadioButton1))
                .addContainerGap(49, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(64, 64, 64)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel1))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2)
                    .addComponent(jComboBox2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jComboBox3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel3))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jComboBox4, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel4))
                .addGap(18, 18, 18)
                .addComponent(jRadioButton1)
                .addContainerGap(82, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>                        

    private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        // TODO add your handling code here:
    }                                          

    private void jRadioButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                              
        // TODO add your handling code here:
    }                                             

    public static void main(String args[]) {
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(print_cheque.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(print_cheque.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(print_cheque.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(print_cheque.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new print_cheque().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JComboBox<String> jComboBox1;
    private javax.swing.JComboBox<String> jComboBox2;
    private javax.swing.JComboBox<String> jComboBox3;
    private javax.swing.JComboBox<String> jComboBox4;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JRadioButton jRadioButton1;
}

Answer 1

Try this

import java.beans.Statement;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.util.logging.Level;

import java.util.logging.Logger;

import javax.swing.JComboBox;

import javax.swing.JOptionPane;

/**
 *
 * @author Sher Sodha
 */
public class NewJFrame extends javax.swing.JFrame {

    /**
     * Creates new form NewJFrame
     */
    Connection con = null;
    java.sql.Statement stmt = null;

    public NewJFrame() throws ClassNotFoundException, SQLException {
        initComponents();
        Class.forName("oracle.jdbc.driver.OracleDriver");
        con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:ora10g", "payablek", "payablek");
        System.out.println("connection successful");
        String query = "Select bnk_nm from d_bank_mst";
        java.sql.Statement st = con.createStatement();
        ResultSet rs = st.executeQuery(query);

        while (rs.next()) {
            String bank = rs.getString(1);
            jComboBox1.addItem(bank);
        }

        rs.close();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jComboBox1 = new javax.swing.JComboBox<>();
        jComboBox2 = new javax.swing.JComboBox<>();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        getContentPane().setLayout(null);

        jComboBox1.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 1", "Item 2", "Item3", "Item 4" }));
        jComboBox1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jComboBox1ActionPerformed(evt);
            }
        });
        getContentPane().add(jComboBox1);
        jComboBox1.setBounds(60, 32, 56, 20);

        jComboBox2.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));
        getContentPane().add(jComboBox2);
        jComboBox2.setBounds(50, 100, 56, 20);

        pack();
    }// </editor-fold>                        

    private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt) {                                           

        JOptionPane.showConfirmDialog(null, "ello");       // TODO add your handling code here:
        JComboBox cb = (JComboBox) evt.getSource();

        String banknm = (String) cb.getSelectedItem();
        JOptionPane.showMessageDialog(null, banknm);

        try {
            stmt = con.createStatement();
        } catch (SQLException ex) {
            Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, null, ex);
        }

        ResultSet rs2 = null;

        String Query = "Select  colouumNafromme  from tablename where bnk_nm=" + banknm + " ";
        try {
            rs2 = stmt.executeQuery(Query);
        } catch (SQLException ex) {
            Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, null, ex);
        }
        try {
            while (rs2.next()) {
                try {
                    jComboBox2.addItem(rs2.getString(1));
                } catch (SQLException ex) {
                    Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        } catch (SQLException ex) {
            Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, null, ex);
        }


    }                                          

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    new NewJFrame().setVisible(true);
                } catch (ClassNotFoundException ex) {
                    Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, null, ex);
                } catch (SQLException ex) {
                    Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        });
    }

---

    // Variables declaration - do not modify                     
    private javax.swing.JComboBox<String> jComboBox1;
    private javax.swing.JComboBox<String> jComboBox2;
    // End of variables declaration                   
}

Answer 2

There are several methods in JComboBox like getSelectedItem(), getSelectedIndex() which can be used to fetch and manipulate data from them and also you can register the JComboBox with ActionListener.

For e.g.

jComboBox1.addActionListener(new ActionListener() {

    @Override
    public void actionPerformed(ActionEvent event) {
        JComboBox<String> jComboBox2 = (JComboBox<String>) event.getSource();
        String str = (String) jComboBox2.getSelectedItem();

        if (str.equals("A")) {
            System.out.println("AAA");
        } else if (str.equals("B")) {
            System.out.println("BBB!");
        }
    }
});

Answer 3

PSEUDO-CODE all of this happens inside the ActionListener

• The ActionListener for jComboBox1 needs to call jComboBox1.getSelectedItem()
• The string (or whatever the object type of jComboBox1) can be used to get the list of applicable Accounts from the database.
• Call jComboBox2.removeAllItems() to empty jComboBox2
• For each Account in the list call jComboBox2.addItem(Account)