java - Refreshing JList in GUI on button event -

i've looked online how update jlist after adding model. automatically, others have manually it. i've tried both, , haven't had success. i'm trying update model addelement method, , goes through. i've walked through code , passed correctly. gui doesn't refresh.

package com.user.tutorial;  import java.awt.eventqueue;  import javax.swing.jframe; import javax.swing.jpanel;  import java.awt.borderlayout;  import javax.swing.jbutton;  import java.awt.event.actionlistener; import java.awt.event.actionevent;  import javax.swing.defaultlistmodel; import javax.swing.jmenubar; import javax.swing.jmenuitem; import javax.swing.box; import javax.swing.jmenu; import javax.swing.jtextpane; import javax.swing.listselectionmodel;  import java.awt.component; import java.awt.color; import java.awt.dimension; import java.awt.font; import java.awt.gridlayout;  import javax.swing.jlabel; import javax.swing.boxlayout; import javax.swing.jlist; import javax.swing.abstractlistmodel;  import java.awt.gridbaglayout; import java.awt.gridbagconstraints; import java.awt.systemcolor; import java.awt.insets; import java.util.list;  public class window {      private jframe frame;      public static void main(string[] args) {         eventqueue.invokelater(new runnable() {             public void run() {                 try {                     window window = new window();                     window.frame.setvisible(true);                 } catch (exception e) {                     e.printstacktrace();                 }             }         });     } public window() {     initialize(); }  /**  * initialize contents of frame. window builder  * generate code.  */ public void addto(jpanel displaypanel, component contenttoadd) {     displaypanel.add(contenttoadd); }  public void initialize() {      dimension sidepanelsize = new dimension(180, 540);      frame = new jframe();     frame.setbounds(100, 100, 480, 540);     frame.setdefaultcloseoperation(jframe.exit_on_close);      jmenubar menubar = new jmenubar();     frame.setjmenubar(menubar);      jmenu mnfile = new jmenu("file");     menubar.add(mnfile);      jmenuitem mntmload = new jmenuitem("load");     mnfile.add(mntmload);      jmenuitem mntmsave = new jmenuitem("save");     mnfile.add(mntmsave);      jmenuitem mntmexit = new jmenuitem("exit");     mnfile.add(mntmexit);      final jpanel itempanel = new jpanel();     itempanel.setpreferredsize(sidepanelsize);     itempanel.setbackground(color.white);     itempanel.setlayout(new borderlayout());      defaultlistmodel<string> model = new defaultlistmodel<>();     (string items : new string [] {"case", "motherboard", "cpu", "gpu", "psu", "ram", "hdd"})         model.addelement(items);      final jlist<string> itemlist = new jlist<>();     itemlist.setmodel(model);      itemlist.setselectionmode(listselectionmodel.single_selection);     itemlist.setfont(new font("segoeui", font.bold, 11));     itempanel.add(itemlist, borderlayout.west);     frame.getcontentpane().add(itempanel, borderlayout.west);      final jlist<string> addtolist = new jlist<>(new defaultlistmodel<string>());      jpanel buttoncontainer = new jpanel();     jpanel buttonlist = new jpanel();     gridbagconstraints c = new gridbagconstraints();      buttonlist.setlayout(new boxlayout(buttonlist, boxlayout.y_axis));     buttoncontainer.setlayout(new gridbaglayout());     buttoncontainer.setbackground(new color(238, 238, 238));      final jpanel displaypanel = new jpanel();     displaypanel.setpreferredsize(sidepanelsize);     displaypanel.setbackground(color.white);     frame.getcontentpane().add(displaypanel, borderlayout.east);                   // right here button action. `displaymodel` model of `jlist` i'm updating.          jbutton addbutton = new jbutton(">>");         addbutton.addactionlistener(new actionlistener() {             public void actionperformed(actionevent e) {                 list<string> selected = itemlist.getselectedvalueslist();                 defaultlistmodel<string> displaymodel = (defaultlistmodel<string>) addtolist.getmodel();                  (string item: selected) {                     displaymodel.addelement(item);                 }             }         });         buttonlist.add(addbutton);           jbutton deletebutton = new jbutton("<<");         deletebutton.addactionlistener(new actionlistener() {             public void actionperformed(actionevent e) {             }         });         buttonlist.add(deletebutton);         c.gridx = 0;         c.gridy = 0;         buttoncontainer.add(buttonlist, c);         frame.getcontentpane().add(buttoncontainer, borderlayout.center);     } } 

i'm not sure going wrong. i've checked documentation. guess i'm missing simple. help.

everything seems passed there isn't change gui.

did read point "3" of suggestion of possible problems?