Bug 312959 [Import/Export] importing file from big disk hangs UI
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/wizards/datatransfer/WizardFileSystemResourceImportPage1.java
if (sourceDirectory == null) {
            setMessage(SOURCE_EMPTY_MESSAGE);
            enableButtonGroup(false);
            return false;
        }
        if (sourceConflictsWithDestination(new Path(sourceDirectory.getPath()))) {
        	setMessage(null);
            setErrorMessage(getSourceConflictMessage());
            enableButtonGroup(false);
            return false;
        }
        List resourcesToExport = selectionGroup.getAllWhiteCheckedItems();
        if (resourcesToExport.size() == 0){
        	setMessage(null);
        	setErrorMessage(DataTransferMessages.FileImport_noneSelected);
        	return false;
        }
        IContainer container = getSpecifiedContainer();
        if (container != null && container.isVirtual()) {
        	if (ResourcesPlugin.getPlugin().getPluginPreferences().getBoolean(ResourcesPlugin.PREF_DISABLE_LINKING)) {
	        	setMessage(null);
	        	setErrorMessage(DataTransferMessages.FileImport_cannotImportFilesUnderAVirtualFolder);
				return false;
        	}
        	if (createLinksInWorkspaceButton == null || createLinksInWorkspaceButton.getSelection() == false) {
	        	setMessage(null);
	        	setErrorMessage(DataTransferMessages.FileImport_haveToCreateLinksUnderAVirtualFolder);
				return false;
        		
        	}