Schedules this {@code SwingWorker} for execution on a
workerthread. There are a number of
worker threads available. In the event all
worker threads are busy handling other {@code SwingWorkers} this {@code SwingWorker} is placed in a waitingqueue.
Note: {@code SwingWorker} is only designed to be executed once. Executing a{@code SwingWorker} more than once will not result in invoking the{@code doInBackground} method twice.