got error when accessing method in another class java

Question

I had Error like this

Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at tugasakhir.Home.TambahActionPerformed(Home.java:285)
at tugasakhir.Home.access$300(Home.java:14)
at tugasakhir.Home$4.actionPerformed(Home.java:97)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$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 org.GNOME.Accessibility.AtkWrapper$6.dispatchEvent(AtkWrapper.java:715)
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)

and this is my code

TugasAkhir.java

package tugasakhir;

public class TugasAkhir {

public static Home hm=new Home();
public static DataCore dt=new DataCore();

public static void main(String[] args) {
    hm.setVisible(true);
    hm.pack();
    hm.setLocationRelativeTo(null);
    hm.setDefaultCloseOperation(Home.EXIT_ON_CLOSE);
    
    dt.setVisible(true);
    dt.pack();
    dt.setLocationRelativeTo(null);
    dt.setDefaultCloseOperation(DataCore.EXIT_ON_CLOSE);
    dt.setState(1);
  }
}

DataCore.java

    Home hm=TugasAkhir.hm;

    public int SearchTable(int j,String query){
        for (int k = 0; k < Tables.getRowCount(); k++) {
            if(Pattern.matches(".*"+query+".*", (String)Tables.getValueAt(k, j))){
                System.out.println("Row: "+k+", Col: "+j);
                return k;
            }
        }
        return 0;
    }
    
    public void check(){
        System.out.print(Tables.getValueAt(0, 1));
    }
    
    public String GetValue(int j, int k){
        return (String)Tables.getValueAt(j, k);
    }
    public int GetInt(int j, int k){
        return (Integer)Tables.getValueAt(j, k);
    }
    
    public void SetValue(int value, int j, int k){
        Tables.setValueAt(value, j, k);
    }
    
    public void tambahini(String Nama, int jumlah){
        int harga = 121;
        javax.swing.table.DefaultTableModel model = (javax.swing.table.DefaultTableModel) hm.Tabl.getModel();
        model.addRow(new Object[]{Nama, harga, jumlah, harga * jumlah});
    }
    
  
    
    private void TambahActionPerformed(java.awt.event.ActionEvent evt) {                                       
        javax.swing.table.DefaultTableModel model = (javax.swing.table.DefaultTableModel) Tables.getModel();
        String nama = Nama.getText();
        Integer jumlah = Integer.valueOf(Jumlah.getText());
        Integer harga = Integer.valueOf(Harga.getText());
        model.addRow(new Object[]{nama, harga, jumlah,});
    }                                      

    private void KembaliActionPerformed(java.awt.event.ActionEvent evt) {                                        
        // TODO add your handling code here:
        Home hm = TugasAkhir.hm;
        hm.setState(0);
        this.setState(1);
    }                                       

    private void HapusActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        javax.swing.table.DefaultTableModel model = (javax.swing.table.DefaultTableModel) Tables.getModel();
        model.removeRow(Tables.getSelectedRow());
    }                                                                  

    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(DataCore.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(DataCore.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(DataCore.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(DataCore.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new DataCore().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton Hapus;
    private javax.swing.JTextField Harga;
    private javax.swing.JTextField Jumlah;
    private javax.swing.JButton Kembali;
    private javax.swing.JTextField Nama;
    public javax.swing.JTable Tables;
    private javax.swing.JButton Tambah;
    private javax.swing.JButton Ubah;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JScrollPane jScrollPane1;
    // End of variables declaration                   
}

Home.java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package tugasakhir;

import java.util.regex.Pattern;
public class Home extends javax.swing.JFrame {
    DataCore dc = TugasAkhir.dt;

    public void addItemsinTable(String nama, int harga, int jumlah){
        javax.swing.table.DefaultTableModel model = (javax.swing.table.DefaultTableModel) this.Tabl.getModel();
        model.addRow(new Object[]{nama, harga, jumlah, harga * jumlah});
    }

    private void TambahActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here
        
        //Inisialisasi Variable\
        String nama = Nama.getText();
        int jumlah = Integer.valueOf(Jumlah.getText());
        
        //Kirim data
        dc.tambahini(nama,jumlah);
        
    }                                      

    private void BersihActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here:
        Nama.setText("");
        Jumlah.setText("");
        Total.setText("");
        Bayar.setText("");
        
    }                                      

    private void LihatActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        DataCore dt = TugasAkhir.dt;
        dt.setState(0);
        this.setState(1);
        
    }                                     
    
    private void OKActionPerformed(java.awt.event.ActionEvent evt) {                                   
        // TODO add your handling code here:
        dc.check();
    }                                  


    private void HapusActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
        javax.swing.table.DefaultTableModel model = (javax.swing.table.DefaultTableModel) Tabl.getModel();
        model.removeRow(Tabl.getSelectedRow());
    }                                     

    private void jScrollPane1MouseClicked(java.awt.event.MouseEvent evt) {                                          
        // TODO add your handling code here:
    }                                         

    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(Home.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(Home.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(Home.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(Home.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() {
                new Home().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JTextField Bayar;
    private javax.swing.JButton Bersih;
    private javax.swing.JButton Hapus;
    private javax.swing.JTextField Jumlah;
    private javax.swing.JButton Lihat;
    private javax.swing.JTextField Nama;
    private javax.swing.JButton OK;
    public javax.swing.JTable Tabl;
    private javax.swing.JButton Tambah;
    private javax.swing.JTextField Total;
    private javax.swing.JButton Ubah;
    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.JScrollPane jScrollPane1;
    private java.awt.Menu menu1;
    private java.awt.Menu menu2;
    private java.awt.PopupMenu popupMenu1;
    // End of variables declaration                   
}

i always have error when using method in another class i had try to get some values in jtable and send it to another class sorry this is my first question in there and i dont know it have limited string so i cut code from netbeans jframe Thanks

Nama or Julmah could be Null in `TambahActionPerformed` of `Home` — sanjeevRm, Jul 03 '21 at 06:09
i add nama and jumlah in Home and process it with DataCore and then get string from jtable in DataCore and send add more row to Home.tabl — John Shon, Jul 03 '21 at 06:52

score 0 · Answer 1 · answered Jul 03 '21 at 06:36

0

your stack trace states that the NullPointerException is thrown at tugasakhir.Home.TambahActionPerformed(Home.java:285) so the error is in one of these lines:

    private void TambahActionPerformed(java.awt.event.ActionEvent evt) {                                       
        // TODO add your handling code here
        
        //Inisialisasi Variable\
        String nama = Nama.getText();
        int jumlah = Integer.valueOf(Jumlah.getText());
        
        //Kirim data
        dc.tambahini(nama,jumlah);
        
    }

Exactly in the line #285 but since I don't know which line it is, I'd need to know which one is the line 285 in your file.

answered Jul 03 '21 at 06:36

bichoFlyer

178
9

dc.tambahini it refered to public void tambahini(String Nama, int jumlah){ int harga = 121; javax.swing.table.DefaultTableModel model = (javax.swing.table.DefaultTableModel) hm.Tabl.getModel(); model.addRow(new Object[]{Nama, harga, jumlah, harga * jumlah}); } – John Shon Jul 03 '21 at 06:44
Ok, some reason, at this point dc is null, may be dc or dt value is changed to null. I'd add a final keyword to dt, so `public static final DataCore dt = new DataCore();` If you inadvertently are changing the value of dt, you'll have a compile error. If not, try doing the same to dc. The error is in Home.java, not in DataCore. – bichoFlyer Jul 03 '21 at 07:01

got error when accessing method in another class java

1 Answers1