Ecco il codice completo del file MyDBConn.java (ditemi se serve anche il file che richiama la funzione):
codice:
package cc;

import java.sql.*;

public class MyDBConn {
    private Connection myConnection;
    private java.sql.Statement stmt;
    
        
    /** Creates a new instance of MyDBConn */
    public MyDBConn() {
    }
    
    public void init(){
    
       try{
        Class.forName("Driver");
        myConnection=DriverManager.getConnection(
                "URL", "user", "pass"
                );
        }
        catch(Exception es){
            alerts.showErr(es.getMessage());
            
        }
    }
    

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

    ///////////// RESULT
    
    
    public Connection getMyConnection(){
        return myConnection;
    }
     
    public void close(ResultSet rs){
        
        if(rs !=null){
            try{
               rs.close();
            }
            catch(Exception e){}
        
        }
    }
    
     public void close(java.sql.Statement stmt){
        
        if(stmt !=null){
            try{
               stmt.close();
            }
            catch(SQLException e){}
            System.out.println("ERRORE");
        }
    }
     
  public void destroy(){
  
    if(myConnection !=null){
    
         try{
               myConnection.close();
            }
            catch(Exception e){}
        
        
    }
  }   
}
E questo è l'output:
codice:
java.lang.NullPointerException
        at cc.MyDBConn.getResultFromPazienti2(MyDBConn.java:51) (corrisponde alla riga rossa del file sopra)
        at cc.Paziente.formWindowOpened(Paziente.java:522)
        at cc.Paziente.access$000(Paziente.java:14)
        at cc.Paziente$2.windowOpened(Paziente.java:108)
        at java.awt.Window.processWindowEvent(Window.java:1187)
        at javax.swing.JFrame.processWindowEvent(JFrame.java:266)
        at java.awt.Window.processEvent(Window.java:1148)
        at java.awt.Component.dispatchEventImpl(Component.java:3955)
        at java.awt.Container.dispatchEventImpl(Container.java:2024)
        at java.awt.Window.dispatchEventImpl(Window.java:1778)
        at java.awt.Component.dispatchEvent(Component.java:3803)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at cc.Paziente.formWindowOpened(Paziente.java:525)
        at cc.Paziente.access$000(Paziente.java:14)
        at cc.Paziente$2.windowOpened(Paziente.java:108)
        at java.awt.Window.processWindowEvent(Window.java:1187)
        at javax.swing.JFrame.processWindowEvent(JFrame.java:266)
        at java.awt.Window.processEvent(Window.java:1148)
        at java.awt.Component.dispatchEventImpl(Component.java:3955)
        at java.awt.Container.dispatchEventImpl(Container.java:2024)
        at java.awt.Window.dispatchEventImpl(Window.java:1778)
        at java.awt.Component.dispatchEvent(Component.java:3803)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)