netbeans - Adding a component to jPanel java -

i'm trying add jtable component jpanel unable see it. doing wrong?.

table gui = new table(data,colum);  mainpanel.add(gui.table);  class table extends jframe {     public jtable table;       public table(vector data, vector colum)     {         setlayout(new flowlayout());          table = new jtable(data,colum);         table.setpreferredscrollableviewportsize(new dimension(900,10));         table.setfillsviewportheight(true);         jscrollpane scrollpane = new jscrollpane(table);         add(scrollpane);      }  } 

extending jframe seems odd; don't use of top level container capabilities. here's example extends jpanel, main() drops panel jframe.

--edited accept existing jpanel

public class tablepanel {   public static void addtabletopanel(jpanel jpanel, vector rowdata, vector columnnames)   {     jtable jtable = new jtable(rowdata, columnnames);     jtable.setfillsviewportheight(true);      jscrollpane jscrollpane = new jscrollpane(jtable);     jscrollpane.setpreferredsize(new dimension(300, 50));      jpanel.add(jscrollpane);   }    public static void main(string[] args) throws exception   {     swingutilities.invokeandwait(new runnable()     {       @override       public void run()       {         vector cols = new vector();         vector rows = new vector();         vector row1 = new vector();          cols.add("a");         cols.add("b");         cols.add("c");         row1.add("1");         row1.add("2");         row1.add("3");         rows.add(row1);         rows.add(row1.clone());         rows.add(row1.clone());         rows.add(row1.clone());          jframe frame = new jframe("tabletest");         frame.setdefaultcloseoperation(jframe.exit_on_close);          jpanel jpanel = new jpanel();         jpanel.setlayout(new borderlayout(0, 0));         tablepanel.addtabletopanel(jpanel, rows, cols);          frame.getcontentpane().add(jpanel);         frame.pack();         frame.setvisible(true);       }     });   } }