awt - Java- Toolkit.getLockingState not updating -

i trying make simple robot program needs know if scroll lock on. read different question , pointed toolkit.getlockingkeystate(). however, method correctly tells whether scoll lock on when started program, refuses update when scroll lock changed. here code:

import java.awt.toolkit;  import java.awt.event.keyevent;   /**  * @author luke senseney  *  */ public class mouse {     /**      * @param args       */     public static void main(string[] args)     {         toolkit t=toolkit.getdefaulttoolkit();         while(true)         {             t.sync();             system.out.println(t.getlockingkeystate(keyevent.vk_num_lock));             try             {                 thread.sleep(1000);             }catch(interruptedexception e)             {                 e.printstacktrace();             }         }     } } 

this version works advertised. expect difference code requests state within event dispatch thread (though cannot explain why case).

import java.awt.*; import java.awt.event.*; import javax.swing.*; import javax.swing.border.emptyborder;  public class checklockingstate {      private jcomponent ui = null;      checklockingstate() {         initui();     }      public void initui() {         if (ui != null) {             return;         }          ui = new jpanel(new borderlayout(4, 4));         ui.setborder(new emptyborder(4, 4, 4, 4));          final jlabel l = new jlabel("click button check locking state..");         ui.add(l, borderlayout.page_start);          final toolkit t = toolkit.getdefaulttoolkit();          actionlistener checkstatelistener = new actionlistener() {              @override             public void actionperformed(actionevent e) {                 boolean b = t.getlockingkeystate(keyevent.vk_num_lock);                 system.out.println(b);                 l.settext("" + b);             }         };          jbutton b = new jbutton("check locking state");         b.addactionlistener(checkstatelistener);         ui.add(b);     }      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) {                 }                 checklockingstate o = new checklockingstate();                  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);     } }