java - JCheckBox not appearing -

i have checked everwhere fix nothing can work make checkbox appear. added panel , added panel window. button appearing must problem checkbox. here code:

import java.awt.borderlayout; import java.awt.dimension; import java.awt.point; import java.awt.toolkit; import java.awt.event.keyevent;  import javax.swing.jbutton; import javax.swing.jcheckbox; import javax.swing.jframe; import javax.swing.jpanel;  public class mainapplication {      public static toolkit tk = toolkit.getdefaulttoolkit();      public static void main(string[] args) {         mainapplication instance = new mainapplication();         instance.start();     }      private jframe window;     private jpanel mainpanel;     private jpanel contingencypanel;      private jbutton applybutton = new jbutton("apply changes");     private jcheckbox autoredlightbox = new jcheckbox("red light");     private jcheckbox autoyellowlightbox = new jcheckbox("yellow light");     private jcheckbox autogreenlightbox = new jcheckbox("green light");     private jcheckbox autobluelightbox = new jcheckbox("blue light");      public void start() {         window = new jframe("main control window");         mainpanel = new jpanel();         contingencypanel = new jpanel();          window.setsize(1280, 720);         window.setresizable(false);         window.setfocusable(true);         window.setfocustraversalkeysenabled(true);         int screenwidth = (int)tk.getscreensize().getwidth();         int screenheight = (int)tk.getscreensize().getheight();         window.setlocation((screenwidth/2)-(window.getwidth()/2), (screenheight/2)-(window.getheight()/2));         window.setdefaultcloseoperation(jframe.exit_on_close);          mainpanel.setlayout(null);         contingencypanel.setlayout(null);          applybutton.settooltiptext("changes applied arduino.");         applybutton.setsize(new dimension(120, 30));         applybutton.setlocation(new point((1280-120)-10, (720-56)-10));          autoredlightbox.setselected(true);         autoredlightbox.setlocation(new point(30, 30));         autoredlightbox.setmnemonic(keyevent.vk_r);          mainpanel.add(applybutton);         mainpanel.add(autoredlightbox, borderlayout.center);          window.add(mainpanel);         window.setvisible(true);     } } 

desired outcome:

that's suited gridlayout.

import java.awt.*; import javax.swing.*; import javax.swing.border.emptyborder;  public class buttonsandchecks {      private jcomponent ui = null;      buttonsandchecks() {         initui();     }      public void initui() {         if (ui!=null) return;          // adjust last 2 numbers need..         ui = new jpanel(new gridlayout(0,5,20,20));         ui.setborder(new emptyborder(4,4,4,4));          // adjust numbers need..         (int i=1; i<26; i++) {             ui.add(new jbutton("button " + i));         }         // adjust numbers need..         (int i=1; i<26; i++) {             ui.add(new jcheckbox("check " + i, i%2==0));         }     }      public jcomponent getui() {         return ui;     }      public static void main(string[] args) {         runnable r = new runnable() {             @override             public void run() {                 try {                     uimanager.setlookandfeel(uimanager.getsystemlookandfeelclassname());                 } catch (exception usedefault) {                 }                 buttonsandchecks o = new buttonsandchecks();                  jframe f = new jframe(o.getclass().getsimplename());                 f.setdefaultcloseoperation(jframe.dispose_on_close);                 f.setlocationbyplatform(true);                  f.setcontentpane(o.getui());                 f.pack();                 f.setminimumsize(f.getsize());                  f.setvisible(true);             }         };         swingutilities.invokelater(r);     } }