Time for action – using null progress monitors and sub monitors

When a method uses progress monitors extensively, it is inelegant to keep checking whether the monitor is null or not. Instead, the progress monitor can be replaced with a NullProgressMonitor, which acts as a no-op for all monitor calls.

1. Update the checkDozen to use a NullProgressMonitor if null is passed:

   private void checkDozen(IProgressMonitor monitor) {
     if (monitor == null)
       monitor = new NullProgressMonitor();

   This allows the remainder of the method to run without modification and saves any NullPointerException errors that may result.

2. A similar result to both the NullProgressMonitor and a SubProgressMonitor with a wrapper/factory class called SubMonitor. This provides factory methods to wrap the monitor and create child progress monitors:

   protected IStatus run(IProgressMonitor monitor) {
     try {
       SubMonitor subMonitor = 
         SubMonitor.convert(monitor,"Preparing", 5000);
       for (int i = 0; i < 50 && !subMonitor...