0
Exception in thread "main" java.lang.NullPointerException
    at tab.setTable(tab.java:36)

My code:

import java.awt.;
import javax.swing.;
import javax.swing.table.;
import java.awt.event.;
import javax.swing.;
import javax.swing.event.;
import java.net.*;
public class tab extends JFrame 
{
    int a;
    JTable jt;
    Container c;
    static int k = 0;
    static int l = 0;
    static DefaultTableModel df;

    tab() 
    {
        df = new DefaultTableModel(50, 0);
        jt = new JTable(df);
        df.addColumn("Request");
        df.addColumn("Acknowledgement");
        jt.setAutoResizeMode(JTable.AUTO_RESIZE_ALL_COLUMNS);
        c = getContentPane();
        JScrollPane jsp = new JScrollPane(jt);
        c.add(jsp);
        setVisible(true);
        setSize(800, 800);
    }

    static void setTable(String s) {
        df.setValueAt(s, k, 0);
        k++;
    }

    static void setTable1(String s) {
        df.setValueAt(s, l, 1);
        l++;
    }

}
Eran
  • 387,369
  • 54
  • 702
  • 768
vineeth reddy
  • 11

1 Answers1

1

If df should be static (as it is now), you shouldn't initialize it in the constructor (which initializes an instance of the class).

Initialize it in a static block instead :

static 
{
    df = new DefaultTableModel(50, 0);
}
Eran
  • 387,369
  • 54
  • 702
  • 768