UIJob是Job的子类，对Job进行简单的封装，使得方法都在asyncDisplay.asyncExec() 上运行

UIJob是Job的子类，对Job进行简单的封装，使得方法都在asyncDisplay.asyncExec() 下运行
以下为UIJob的源码，关键在run方法中的
asyncDisplay.asyncExec(new Runnable() {...}

public abstract classUIJob extends Job {
    private Display cachedDisplay;
    public UIJob(String name) {
        super(name);
    }
    public UIJob(Display jobDisplay, String name) {
        this(name);
        setDisplay(jobDisplay);
    }

    public static IStatus errorStatus(Throwable exception) {
        return WorkbenchPlugin.getStatus(exception); 
    }
    public final IStatus run(final IProgressMonitor monitor) {
        if (monitor.isCanceled()) {
            return Status.CANCEL_STATUS;
       }
        Display asyncDisplay = getDisplay();
        if (asyncDisplay == null || asyncDisplay.isDisposed()) {
            return Status.CANCEL_STATUS;
        }
        asyncDisplay.asyncExec(new Runnable() {
            public void run() {
                IStatus result = null;
                Throwable throwable = null;
                try {
                    //As we are in the UI Thread we can
                    //always know what to tell the job.
                    setThread(Thread.currentThread());
                    if (monitor.isCanceled()) {
                         result = Status.CANCEL_STATUS;
                    } else {
                        UIStats.start(UIStats.UI_JOB, getName());
                        result = runInUIThread(monitor);
                    }

                } catch(Throwable t){
                 throwable = t;
                } finally {
                 UIStats.end(UIStats.UI_JOB, UIJob.this, getName());
                    if (result == null) {
                                 result = new Status(IStatus.ERROR,
                                PlatformUI.PLUGIN_ID, IStatus.ERROR,
                                ProgressMessages.InternalError,
                                throwable);
                     }
                    done(result);
                }
            }
        });
        return Job.ASYNC_FINISH;
    }

    public abstract IStatus runInUIThread(IProgressMonitor monitor);

    public void setDisplay(Display runDisplay) {
        Assert.isNotNull(runDisplay);
        cachedDisplay = runDisplay;
    }

    public Display getDisplay() {
        //If it was not set get it from the workbench
        if (cachedDisplay == null && PlatformUI.isWorkbenchRunning()) {
               return PlatformUI.getWorkbench().getDisplay();
         }
        return cachedDisplay;
    }
}