method always visible by other class

[Mariano]

Then I have a class called MyDBConn.java, inside this class there's a
method called GetResultFromPazienti():

MyDBConn.java:
==================================

package cc;

import java.sql.*;

public class MyDBConn {
private Connection myConnection;
private java.sql.Statement stmt;

// ...

public ResultSet getResultFromPazienti2(String query) {
ResultSet rs=null;
try{
rs=stmt.executeQuery(query);
}
catch(Exception e){
alerts.showErr(e.getMessage());
}
return rs;
}

// ...

==================================

After this, I have a class called Paziente.java, from this class I
would call method: getResultFromPazienti2(), class is something like
this:

File: Paziente.java
==================================
package cc;
import java.sql.*;

public class Paziente extends javax.swing.JFrame {
private MyDBConn mdbc;
private java.sql.Statement stmt;

// ...
// ...

private void formWindowOpened(java.awt.event.WindowEvent evt)
{
ResultSet rs=mdbc.getResultFromPazienti2("select ... from ...
where ...");

try {
rs.next();
// ...
txtNome.setText(rs.getString("NOME"));
// ...
} catch (SQLException ex) {
ex.printStackTrace();
}
}
}


==================================

At first moment seem that are not problems, infact there's no problem
in compile time, but when I execute project and method
formWindowOpened() is started an "Exception in thread "AWT-
EventQueue-0" java.lang.NullPointerException", where are the
problems???
Thank you to all....

 

[Brandon McCombs]

Then I have a class called MyDBConn.java, inside this class there's a
method called GetResultFromPazienti():

The method below is called GetResultFromPazienti2().

MyDBConn.java:
==================================

package cc;

import java.sql.*;

public class MyDBConn {
private Connection myConnection;
private java.sql.Statement stmt;

// ...

the method below is not the same as you specify above.
You never instantiate stmt so maybe that is what is producing the null
pointer.

public ResultSet getResultFromPazienti2(String query) {
ResultSet rs=null;
try{
rs=stmt.executeQuery(query);
}
catch(Exception e){
alerts.showErr(e.getMessage());
}
return rs;
}

// ...

==================================

After this, I have a class called Paziente.java, from this class I
would call method: getResultFromPazienti2(), class is something like
this:

File: Paziente.java
==================================
package cc;
import java.sql.*;

public class Paziente extends javax.swing.JFrame {
private MyDBConn mdbc;
private java.sql.Statement stmt;

Is stmt ever used and initialized?
Is mdbc ever initialized? You leave out code that prevents full analysis
so we can't help you.

// ...
// ...

private void formWindowOpened(java.awt.event.WindowEvent evt)
{
ResultSet rs=mdbc.getResultFromPazienti2("select ... from ...
where ...");

try {
rs.next();
// ...
txtNome.setText(rs.getString("NOME"));
// ...
} catch (SQLException ex) {
ex.printStackTrace();
}
}
}


==================================

At first moment seem that are not problems, infact there's no problem
in compile time, but when I execute project and method
formWindowOpened() is started an "Exception in thread "AWT-
EventQueue-0" java.lang.NullPointerException", where are the
problems???
Thank you to all....

The exception should tell you what line the null pointer is on. Does it?