java - add multiple JPanels in the middle of the window -

i want create input jframe program reads 3 fields (model, week , plan), , after inserting 1 line user can choose input new values on different row, done pressing jlabel image add icon. expectation able add new jpanel (called body in subclass) right under last 1 (jpanel lastcontent global variable), , able remove or add new ones user needs. below code far:

package marquesina;  import java.awt.container; import java.awt.dimension; import java.awt.toolkit; import javax.swing.jbutton; import javax.swing.jframe; import javax.swing.jlabel; import javax.swing.jpanel; import javax.swing.jtextfield; import org.jdesktop.swingx.horizontallayout; import org.jdesktop.swingx.verticallayout;  public class jmodificaciones extends container {  private jpanel lastcontent;  public static void main(string[] args) {     //schedule job event-dispatching thread:     //creating , showing application's gui.     javax.swing.swingutilities.invokelater(() -> {         jframe frame = new jframe("demo");         frame.setdefaultcloseoperation(jframe.exit_on_close);          //set content pane.         jmodificaciones mods = new jmodificaciones();         frame.setcontentpane(mods);          //display window.         frame.pack();         dimension dim = toolkit.getdefaulttoolkit().getscreensize();         frame.setlocation(                 dim.width / 2 - frame.getsize().width / 2,                 dim.height / 2 - frame.getsize().height / 2);         frame.setvisible(true);     }); }  public jmodificaciones() {     initcomponents();     system.out.println("new panel created"); }  private void initcomponents() {     jpanel jheader = new jpanel();     jlabel jlmod = new jlabel();     jlabel jlsem = new jlabel();     jlabel jlplan = new jlabel();     jpanel jfooter = new jpanel();     jbutton jguardar = new jbutton();     jbutton jcancelar = new jbutton();      setlayout(new verticallayout(10));      //header     jheader.setlayout(new horizontallayout());      jlmod.settext("model");     jheader.add(jlmod);      jlweek.settext("week");     jheader.add(jlweek);      jlplan.settext("plan");     jheader.add(jlplan);      add(jheader);      //content     add(new jcontent());      //footer     jguardar.settext("save");     jfooter.add(jguardar);      jcancelar.settext("cancel");     jfooter.add(jcancel);      add(jfooter); }  public class jcontent extends jpanel {      jlabel jadd = new javax.swing.jlabel();     jlabel jdelete = new javax.swing.jlabel();      public jcontent() {         jpanel body = new jpanel(new horizontallayout());         jtextfield jmodel = new jtextfield();         jtextfield jweek = new jtextfield();         jtextfield jplan = new jtextfield();          body.setlayout(new org.jdesktop.swingx.horizontallayout());          jmodel.setpreferredsize(new java.awt.dimension(100, 28));         body.add(jmodel);          jweek.setpreferredsize(new java.awt.dimension(100, 28));         body.add(jweek);          jplan.setpreferredsize(new java.awt.dimension(100, 28));         body.add(jplan);          jadd.seticon(                 new javax.swing.imageicon(                         getclass().getresource("add.png")));         jadd.addmouselistener(new java.awt.event.mouseadapter() {             @override             public void mouseclicked(java.awt.event.mouseevent evt) {              }         });         body.add(jadd);          jdelete.seticon(                 new javax.swing.imageicon(                         getclass().getresource("delete.png")));         jdelete.addmouselistener(new java.awt.event.mouseadapter() {             @override             public void mouseclicked(java.awt.event.mouseevent evt) {                 remove(lastcontent);             }         });         body.add(jdelete);          add(body);     } } 

}

however i'm not able add new jpanel (which want create when user clicks on jadd jlabel), can't come way reference jpanel want put new components , using add() or remove() in above code reference mouselistener, not jpanel created in sublcass...