When i am using JavaFX, the sleep function won't work accordingly. Like in this code:

```
public class Controller {

@FXML private Label label;
@FXML private Button b1;

public void write() throws InterruptedException
{
    label.setText("FIRST TIME");
    for(int i=1;i<=5;i++)
    {
        System.out.println("Value "+i);
        label.setText("Value "+i);
        Thread.sleep(2000);
    }
    label.setText("LAST TIME");
}

```

when the Button b1 is pressed the write function is called. Now, in the console "Value + i" is being printed after 2 seconds. But that time the text of Label l1 doesn't change and finally it only changes to "LAST TIME". What is wrong in here ?