java - Need Help Getting A Simple Stop-Watch Working? -

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so experimenting little stop-watch object , can't figure out why isn't working. have gui following; timeinfield jtextfield user enters start time of clock. timerfield jtextfield clock displayed timing. startbutton jbutton user clicks start clock. stopbutton jbutton user clicks stop clock.

right now, timerfield displays running: 0 seconds. nothing else happens, maybe doing wrong first time trying this. start learning how use threads thought might me started.

  private void startbuttonactionperformed(java.awt.event.actionevent evt) {          string starttim = timeinfield.gettext();         long starttime = long.valueof(starttim);         boolean running = false;         timer timer = null;          long time = (system.currenttimemillis() - starttime)/1000;          timerfield.settext("running:" + time + "seconds");         if (running==false) {            running = true;            timerfield.settext("running: 0 seconds");         }         if (stopbutton.isselected()) {             timer.stop();             running = false;             long endtime = evt.getwhen();             double seconds = (endtime - starttime)/1000.0;             timerfield.settext("time: " + seconds + "sec.");         } }

it displays "running: 0 seconds" because after timerfield.settext("running: 0 seconds"); never update gui.

also, attempt perform timer.stop(); while timer null, cause nullpointerexception.

and 1 more thing: running false every time click button, since local variable , initialized false every time. if want permanent, move out of method, , initialize outside.


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