Javanian: First of all, this is not a logical error, it is a run time error. You are most likely trying to utilize a variable you haven't initialized or a variable that points to null hence the 'NullPointerException'. I can't see the rest of your code but i suspect it is comming from the result set variable 'rs'. Check to see if it has been initialized and if it actually holds any value.

uken73: Yes Null Pointer Exception indicates an attempt to access an uninitialized variable and like Javanian has already said, it's most likely the ResultSet rs. Confirm that it has been initialized.

void InitDatabase()
{

   try 
   {
        String host="jdbc:derby://localhost:1527/Employees";
        String uName="admin1";
        String uPass="admin";
        connection cont =DriverManager.getConnection(host,uName,uPass);
        Statement stmtt= cont.CreateStatement();
        String SQL="SELECT * FROM Workers";
        ResultSet rs3=stmtt.executeQuery(SQL);
    }
}

  public YourClassName
  {
        InitDatabase();
  }

try
 {
       rs3.first();
       //get value
       string fname=rs3.getString(Fname);
       //set value
       txtFirstName.setText(fname);
 }

try
 {
       rs3.next();
       //get value
       string fname=rs3.getString(Fname);
       //set value
       txtFirstName.setText(fname);
 }

Capnd143: please help me check the code above! Thanks

//ok i guess i am starting to be a pain in the ass around here, but i seriously am not getting it,
//i have never been stucked so long in a particular problem, its been 4 days now, i have done virtually everything am
// told but keep getting undesired results, dunno whether its related to my java version or what, so am posting my entire code here



//sturborn code begins here


public class Workers extends javax.swing.JFrame {


  
    public Workers() {
        initComponents();
        DoConnect();
    }
 void DoConnect( ) {
  try{    
       String host = "jdbc:derby://localhost:1527/Employees";
String uName = "admin1";
String uPass= "admin";

        Connection cont = DriverManager.getConnection( host, uName, uPass);
        
        Statement    stmtt = cont.createStatement();
        String SQL = "SELECT * FROM Workers";
        ResultSet rs2 = stmtt.executeQuery(SQL);
       rs2.next( );
int id_col = rs2.getInt("ID";
String first_name = rs2.getString("First_Name";
String last_name = rs2.getString("Last_Name";
String job = rs2.getString("Job_Title";
String id = Integer.toString( id_col );
textID.setText(id);
textFirstName.setText(first_name);
textLastName.setText(last_name);
textJobTitle.setText(job);

       
   }
   
  
catch ( SQLException err ) {
System.out.println( err.getMessage( ) );

}
    }

  // crazy button to handle the database naigation begins here
//=======================================================================================//

 private void btnNextActionPerformed(java.awt.event.ActionEvent evt) {                                                
        
        try
        {
             
        
        
         if( rs3.next())           //for some crazy reason my netbeans underlines my rs3 object variable 
                                      //and keeps shouting "cannot find symbol"
           {                         //when i know so well i declared that variable
int id_col = rs3.getInt("ID";
String first_name = rs3.getString("First_Name";
String last_name = rs3.getString("Last_Name";
String job = rs3.getString("Job_Title";
String id = Integer.toString( id_col );


textID.setText(id);
textFirstName.setText(first_name);
textLastName.setText(last_name);
textJobTitle.setText(job);
         
         }
         
         cont.close();
        }
            
catch(SQLException err)           {System.out.println(err.getMessage());}
    
        
    }                                       

Javanian: OKAY, Let's start.

First of all, It is imperative for you to know that creating a connection each time a button is clicked is wrong in every way possible. You should put your connection statements in a method and place it in your constructor. So it establishes a connection as soon as the application starts.

So assuming the method is called InitDatbase()

Your code should be something like

void InitDatabase()
{

   try 
   {
        String host="jdbc:derby://localhost:1527/Employees";
        String uName="admin1";
        String uPass="admin";
        connection cont =DriverManager.getConnection(host,uName,uPass);
        Statement stmtt= cont.CreateStatement();
        String SQL="SELECT * FROM Workers";
        ResultSet rs3=stmtt.executeQuery(SQL);
    }
}

Then you call your InitDatabase() in your constructor like this

  public YourClassName
  {
        InitDatabase();
  }

Okay, i don't really know how you intend to make your app work. So i will touch a possible scenario i can think of. I am going to assume that as soon as the app loads it displays the first user in the database. To do this, you should create a method somewhere and probably call it firstUser();

In your first user method, do this.

void firstUser()
{

try
 {
       rs3.first();
       //get value
       string fname=rs3.getString(Fname);
       //set value
       txtFirstName.setText(fname);
 }

}
Now in your btnNextActionPerformed method, do something like this. This would work for the 'NextUserButton'

try
 {
       rs3.next();
       //get value
       string fname=rs3.getString(Fname);
       //set value
       txtFirstName.setText(fname);
 }

Capnd143:

//ok i guess i am starting to be a pain in the ass around here, but i seriously am not getting it,
//i have never been stucked so long in a particular problem, its been 4 days now, i have done virtually everything am
// told but keep getting undesired results, dunno whether its related to my java version or what, so am posting my entire code here
//sturborn code begins here
public class Workers extends javax.swing.JFrame {
public Workers() {
initComponents();
DoConnect();
}
void DoConnect( ) {
try{
String host = "jdbc:derby://localhost:1527/Employees";
String uName = "admin1";
String uPass= "admin";
Connection cont = DriverManager.getConnection( host, uName, uPass);
Statement stmtt = cont.createStatement();
String SQL = "SELECT * FROM Workers";
ResultSet rs2 = stmtt.executeQuery(SQL);
rs2.next( );
int id_col = rs2.getInt("ID";
String first_name = rs2.getString("First_Name";
String last_name = rs2.getString("Last_Name";
String job = rs2.getString("Job_Title";
String id = Integer.toString( id_col );
textID.setText(id);
textFirstName.setText(first_name);
textLastName.setText(last_name);
textJobTitle.setText(job);
}
catch ( SQLException err ) {
System.out.println( err.getMessage( ) );
}
}
// crazy button to handle the database naigation begins here
//=======================================================================================//
private void btnNextActionPerformed(java.awt.event.ActionEvent evt) {
try
{
if( rs3.next()) //for some crazy reason my netbeans underlines my rs3 object variable
//and keeps shouting "cannot find symbol"
{ //when i know so well i declared that variable
int id_col = rs3.getInt("ID";
String first_name = rs3.getString("First_Name";
String last_name = rs3.getString("Last_Name";
String job = rs3.getString("Job_Title";
String id = Integer.toString( id_col );
textID.setText(id);
textFirstName.setText(first_name);
textLastName.setText(last_name);
textJobTitle.setText(job);
}
cont.close();
}
catch(SQLException err) {System.out.println(err.getMessage());}
}

public class Workers extends javax.swing.JFrame 
{
	ResultSet rs2; //moved here to increase it level of access so that it can be
                           // available in the btnNextActionPerformed event method
	public Workers() {
		initComponents();
		DoConnect();
	}
	void DoConnect( ) {
	Connection cont; //move here to make it available in the catch block for closing
	try{
		String host = "jdbc:derby://localhost:1527/Employees";
		String uName = "admin1";
		String uPass= "admin";
		cont = DriverManager.getConnection( host, uName, uPass); //declaration moved outside try block
		Statement stmtt = cont.createStatement();
		String SQL = "SELECT * FROM Workers";
		rs2 = stmtt.executeQuery(SQL); //declaration moved to class field
		rs2.next( );
		int id_col = rs2.getInt("ID" ) ;
		String first_name = rs2.getString("First_Name" ) ;
		String last_name = rs2.getString("Last_Name" ) ;
		String job = rs2.getString("Job_Title" ) ;
		String id = Integer.toString( id_col ) ;
		textID.setText(id);
		textFirstName.setText(first_name);
		textLastName.setText(last_name);
		textJobTitle.setText(job);
	}
	catch ( SQLException err ) {System.out.println( err.getMessage( ) );	}
	}
	finally{cont.close();}//finally block introduced to handle closing of database connection.

	private void btnNextActionPerformed(java.awt.event.ActionEvent evt) {
		try
		{
                        //rs3 for which I couldn't find it's declaration has been renamed to rs2 
                       //to correspond to rs2 declared as data member
			if( rs2.next()) 
			{ 
				int id_col = rs2.getInt("ID" ) ;
				String first_name = rs2.getString("First_Name" ) ;
				String last_name = rs2.getString("Last_Name" ) ;
				String job = rs2.getString("Job_Title" ) ;
				String id = Integer.toString( id_col) ;
				textID.setText(id);
				textFirstName.setText(first_name);
				textLastName.setText(last_name);
				textJobTitle.setText(job);
			}
			//cont.close(); moved to finally block in DoConnect method.
		}
		catch(SQLException err) {System.out.println(err.getMessage());}
	}
}

uken73: I currently don't have a Java compatible editor on my system to assist me with syntacs errors but I made some modification on your codes with comments and emphasis on the modifications. I hope this solves your problem.

public class Workers extends javax.swing.JFrame 
{
	ResultSet rs2; //moved here to increase it level of access so that it can be
                           // available in the btnNextActionPerformed event method
	public Workers() {
		initComponents();
		DoConnect();
	}
	void DoConnect( ) {
	Connection cont; //move here to make it available in the catch block for closing
	try{
		String host = "jdbc:derby://localhost:1527/Employees";
		String uName = "admin1";
		String uPass= "admin";
		cont = DriverManager.getConnection( host, uName, uPass); //declaration moved outside try block
		Statement stmtt = cont.createStatement();
		String SQL = "SELECT * FROM Workers";
		rs2 = stmtt.executeQuery(SQL); //declaration moved to class field
		rs2.next( );
		int id_col = rs2.getInt("ID" ) ;
		String first_name = rs2.getString("First_Name" ) ;
		String last_name = rs2.getString("Last_Name" ) ;
		String job = rs2.getString("Job_Title" ) ;
		String id = Integer.toString( id_col ) ;
		textID.setText(id);
		textFirstName.setText(first_name);
		textLastName.setText(last_name);
		textJobTitle.setText(job);
	}
	catch ( SQLException err ) {System.out.println( err.getMessage( ) );	}
	}
	finally{cont.close();}//finally block introduced to handle closing of database connection.

	private void btnNextActionPerformed(java.awt.event.ActionEvent evt) {
		try
		{
                        //rs3 for which I couldn't find it's declaration has been renamed to rs2 
                       //to correspond to rs2 declared as data member
			if( rs2.next()) 
			{ 
				int id_col = rs2.getInt("ID" ) ;
				String first_name = rs2.getString("First_Name" ) ;
				String last_name = rs2.getString("Last_Name" ) ;
				String job = rs2.getString("Job_Title" ) ;
				String id = Integer.toString( id_col) ;
				textID.setText(id);
				textFirstName.setText(first_name);
				textLastName.setText(last_name);
				textJobTitle.setText(job);
			}
			//cont.close(); moved to finally block in DoConnect method.
		}
		catch(SQLException err) {System.out.println(err.getMessage());}
	}
}

Notice that I enclosed the code segment in [code][/code] tags so that it can be formatted well for ease of reading the code.

Capnd143: thanks bro, your explanation panned out right, thanks a lot!

Capnd143:
@javanian and all the pros in the house please help me out
i am having problem with navigating a jdbc, in created a button,
and i want the button to load the next record from a datase when clicked
but i keep getting a weird looking logical error when i try it out, this is my code:


private void btnNextActionPerformed(java.awt.event.ActionEvent evt) {
try{while( rs.next( ));
int id_col = rs.getInt("ID";
String first_name = rs.getString("First_Name";
String last_name = rs.getString("Last_Name";
String job = rs.getString("Job_Title";
String id = Integer.toString( id_col );
textID.setText(id);
textFirstName.setText(first_name);
textLastName.setText(last_name);
textJobTitle.setText(job);}
catch(SQLException err){System.out.println(err.getMessage());}


this is the error i get when i run the the application:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Employees.Workers.btnNextActionPerformed(Workers.java:204)
at Employees.Workers.access$200(Workers.java:17)
at Employees.Workers$3.actionPerformed(Workers.java:138)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
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:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:703)
at java.awt.EventQueue.access$000(EventQueue.java:102)
at java.awt.EventQueue$3.run(EventQueue.java:662)
at java.awt.EventQueue$3.run(EventQueue.java:660)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:676)
at java.awt.EventQueue$4.run(EventQueue.java:674)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:673)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)
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