Problem ResultSet in JTable ( - -)""

Question

I have encountered error when compile the code implemented, as i first time write Jtable, it might be a bit messy.
Please advice ..............
import java.sql.Connection;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.*;
import javax.swing.*;
import java.awt.*;
import javax.swing.JTable;
import java.util.*;
import java.io.*;
public class display {
static Statement stmt;
static Connection conn = null;
String msg="Err";
static int c=0;
static String str;
static boolean scrolling= true;
static Statement stat;
static JScrollPane scrollPane;
static ResultSet set;
static ResultSetMetaData rsmd;
static String[] tableColumnsName;
private ArrayList cache;
public void open() {
try {
conn = DB.getConnection();
stmt = conn.createStatement();
} catch(SQLException e) {
System.out.println(e);
public static void main(String[] args)
display dis = new display();
dis.open();
dis.display();
dis.CachingResultSetTableModel();
int r= dis.getRowCount();
Object data=dis.getValueAt (r ,c);
JTable table = new JTable(data,tableColumnsName);
dis.close();
public static void display() {
try {
String st="";
String str="";
ResultSet set = stmt.executeQuery("select * from SYSTEM_USER");
DatabaseMetaData meta= conn.getMetaData();
rsmd= set.getMetaData();
c= getColumnCount();
tableColumnsName= new String[c];
while(set.next()) {
for(int i= 0; i<c; i++)
     tableColumnsName=getColumnName(i);
System.out.println(str);
} catch(SQLException e) {
System.out.println(e);
public static String getColumnName(int c)
try
return rsmd.getColumnName(c+1);
catch(SQLException e)
e.printStackTrace();
return "";
public static int getColumnCount()
try
return rsmd.getColumnCount();
catch(SQLException e)
e.printStackTrace();
return 0;
public void close() {
try {
stmt.close();
} catch(SQLException e) {
System.out.println(e);
try {
conn.close();
} catch(SQLException e) {
System.out.println(e);
public void CachingResultSetTableModel()
try
cache = new ArrayList();
/* place all data in an array list of Object[] arrays
We don't use an Object[][] because we don't know
how many rows are in the result set
while (set.next())
Object[] row = new Object[c];
for (int j = 0; j < row.length; j++)
row[j] = set.getObject(j + 1);
cache.add(row);
catch(SQLException e)
System.out.println("Error " + e);
public Object getValueAt(int r, int c)
if (r < cache.size())
return ((Object[])cache.get(r))[c];
else
return null;
public int getRowCount()
return cache.size();

Answer 1

Its seems like get object no work in my db, the object sound like null.
how i go to extract table data???
Error message
C:\Proj>javac display.java
Note: display.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: display.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
C:\Proj>java display
Exception in thread "main" java.lang.NullPointerException
at display.CachingResultSetTableModel(display.java:143)
at display.main(display.java:42)
import java.sql.Connection;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.*;
import javax.swing.*;
import java.awt.*;
import javax.swing.JTable;
import java.util.*;
import java.io.*;
public class display extends JFrame {
    static Statement stmt;
    static Connection conn = null;
    String msg="Err";
    static int c=0;
    static String str;
    static boolean scrolling= true;
    static Statement stat;
    static JScrollPane scrollPane;
    static ResultSet set;
    static ResultSetMetaData rsmd;
    static String[] tableColumnsName;
    static Vector<Object> cache;
    static JTable table;
   public void open() {
        try {
            conn = DB.getConnection();
            stmt = conn.createStatement();
        } catch(SQLException e) {
            System.out.println(e);
   public static void main(String[] args)
        display dis = new display();
        JFrame frame= new display();
        dis.open();
        dis.display();
        dis.CachingResultSetTableModel();         
        int r= dis.getRowCount();
        Object data=dis.getValueAt (r ,c);
        Vector<Object> newColumnNames = new Vector();
        for(int i=0; i<tableColumnsName.length; i++)
                newColumnNames.add(tableColumnsName);
table = new JTable(cache,newColumnNames);
frame.show();
dis.close();
public void display() {
try {
String st="";
String str="";
ResultSet set = stmt.executeQuery("select * from SYSTEM_USER");
DatabaseMetaData meta= conn.getMetaData();
rsmd= set.getMetaData();
c= getColumnCount();
tableColumnsName= new String[c];
while(set.next()) {
for(int i=0; i<c; i++)
          tableColumnsName[i]=getColumnName(i);
} catch(SQLException e) {
System.out.println(e);
getContentPane().add(new JScrollPane(table));
public static String getColumnName(int c)
try
return rsmd.getColumnName(c+1);
catch(SQLException e)
e.printStackTrace();
return "";
public static int getColumnCount()
try
return rsmd.getColumnCount();
catch(SQLException e)
e.printStackTrace();
return 0;
public void close() {
try {
stmt.close();
} catch(SQLException e) {
System.out.println(e);
try {
conn.close();
} catch(SQLException e) {
System.out.println(e);
public void CachingResultSetTableModel()
try
cache = new Vector();
/* place all data in an array list of Object[] arrays
We don't use an Object[][] because we don't know
how many rows are in the result set
while (set.next())
//create a Vector to hold the data for a single row
Vector<Object> row = new Vector();
//add the column data to the row
for(int i=0; i<tableColumnsName.length; i++)
row.add(set.getObject(i+1));
//add the row data to the Vector for the table rows
cache.add(row);
catch(SQLException e)
System.out.println("Error " + e);
public Object getValueAt(int r, int c)
if (r < cache.size())
return ((Object[])cache.get(r))[c];
else
return null;
public int getRowCount()
return cache.size();