swing - Populate jTable in JAVA -


why have these error? mean? want display data on sql db.

run: exception in thread "awt-eventqueue-0" java.lang.nullpointerexception     @ javaapplication25.searchpatient.<init>(searchpatient.java:26)     @ javaapplication25.searchpatient$2.run(searchpatient.java:146)     @ java.awt.event.invocationevent.dispatch(invocationevent.java:251)     @ java.awt.eventqueue.dispatcheventimpl(eventqueue.java:705)     @ java.awt.eventqueue.access$000(eventqueue.java:101)     @ java.awt.eventqueue$3.run(eventqueue.java:666)     @ java.awt.eventqueue$3.run(eventqueue.java:664)     @ java.security.accesscontroller.doprivileged(native method)     @ java.security.protectiondomain$1.dointersectionprivilege(protectiondomain.java:76)     @ java.awt.eventqueue.dispatchevent(eventqueue.java:675)     @ java.awt.eventdispatchthread.pumponeeventforfilters(eventdispatchthread.java:211)     @ java.awt.eventdispatchthread.pumpeventsforfilter(eventdispatchthread.java:128)     @ java.awt.eventdispatchthread.pumpeventsforhierarchy(eventdispatchthread.java:117)     @ java.awt.eventdispatchthread.pumpevents(eventdispatchthread.java:113)     @ java.awt.eventdispatchthread.pumpevents(eventdispatchthread.java:105)     @ java.awt.eventdispatchthread.run(eventdispatchthread.java:90)

here codes used, don't know how fix because i'm not enough in programming java apps. , can me here? :

package javaapplication25;  /**  *  * @author cleanfuel  */ import java.sql.*; import java.util.vector; import java.util.logging.level; import java.util.logging.logger; import javax.swing.table.defaulttablemodel; public class searchpatient extends javax.swing.jframe {      /**      * creates new form searchpatient      */     public searchpatient() throws sqlexception {         initcomponents();          statement stmt = null;          resultset rs = stmt.executequery("select * dbo.patients");         resultsetmetadata rsmetadata = rs.getmetadata();          int columns = rsmetadata.getcolumncount();          defaulttablemodel dtm = new defaulttablemodel();         vector columns_vector = new vector();         vector rows_vector = new vector();          (int i=1; i< columns; i++){         columns_vector.addelement(rsmetadata.getcolumnname(i));         }          dtm.setcolumnidentifiers(columns_vector);          while (rs.next()){              rows_vector = new vector();             (int j=1; j<columns; j++){                  rows_vector.addelement(rs.getstring(j));             }             dtm.addrow(rows_vector);         }         tblpatients.setmodel(dtm);      }       @suppresswarnings("unchecked")   connection connection;     private void formwindowopened(java.awt.event.windowevent evt) {         // todo add handling code here:         connection = main.connectdatabase();     }

you have these 2 lines, 1 after other 

statement stmt = null;  resultset rs = stmt.executequery("select * dbo.patients");

you've not initialised stmt object, null, nothing, natta

basically, it's trying turn on tv before you've plugged in, it's not work

take @ jdbc data access more details, essentially, need establish connection database , use connection create statement object, can query it.


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