Java timer delay not working properly

Question

I'm trying to use timer delay from the javax.swing.Timer class.
I'm trying to have a label (a temperature) in a JFrame updated every 5 seconds, however the label sometimes gets updated in 1 second. I want it to happen only in 5 seconds.
Here is a portion of my code:

int delay = 5000;           //milliseconds    
ActionListener taskPerformer = new ActionListener() {
                  public void actionPerformed(ActionEvent evt) {
                        tempLabel.setVisible(true);
                        String currTemp = null; //current temperature
                        try {
                            currTemp = getWeatherData.getTemp(locationIndex);
                        } catch (Exception e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                        tempLabel.setText("Temperature :  " + currTemp);
                  }
              };
              Timer timer= new Timer(delay, taskPerformer);
              timer.setRepeats(true);
              timer.start();  

What's happening? Thanks for reading

Answer 1

Haven't used Timer object from swing. But from what i can read, the "delay" you are using, is actually speed?

https://docs.oracle.com/javase/tutorial/uiswing/misc/timer.html

Look into timer.setInitialDelay(pause); instead

//EDIT:

Might have to give it a delay in between every 'successful run' instead of just:

Timer timer= new Timer(delay, taskPerformer); 
timer.setDelay(delay); 
timer.setRepeats(true); 
timer.start(); 

Answer 2

The amount of time can be affected by a number of things. It's important to remember, a Timer is not accurate, it's only suppose to guarantee a minimum amount of time between ticks.

However, because Timer tick within the context of the EDT and I have no idea what getWeatherData.getTemp is actually doing, it's possible that it's blocking the EDT and preventing the UI from been updated ... or a whole bunch of other things in your code which you're not showing us.

It might be better to use a SwingWorker

public class TempatureWorker extends SwingWorker<Void, String> {

    private int locationIndex;

    public TempatureWorker(int locationIndex) {
        this.locationIndex = locationIndex;
    }

    @Override
    protected Void doInBackground() throws Exception {
        while (!isCancelled()) {
            publish(getWeatherData.getTemp(locationIndex));
            Thread.sleep(5000);
        }
        return null;
    }

    @Override
    protected void process(List<String> values) {
        String last = values.get(values.size() - 1);
    }

}

You have to work out how you want to update the UI from here, so long as you're doing from process method. You could pass a reference of the JLabel to the worker, but I'd be tempted to use an observer pattern instead, as it decouples the worker.

See Worker Threads and SwingWorker for more details