EDIT

import eu.etaxonomy.taxeditor.preference.IPreferenceKeys;

import eu.etaxonomy.taxeditor.preference.PreferencesUtil;

        if(PreferencesUtil.getBooleanValue(IPreferenceKeys.SHOW_EXPERIMENTAL_FEATURES)){

            /**

             * Key generation button

             */

            Button btnGenerateKey = new Button(this, SWT.PUSH);

            btnGenerateKey.setText("Generate Polytomous Key");

            btnGenerateKey.addSelectionListener(new SelectionAdapter() {

                @Override

                public void widgetSelected(SelectionEvent e) {

                    if(StoreUtil.promptCheckIsDirty(matrix.getPart())){

                        return;

                    }

                    Set<TaxonNodeDto> nodeDtos = matrix.getDescriptiveDataSet().getTaxonSubtreeFilter().stream()

                            .map(node->new TaxonNodeDto(node))

                            .collect(Collectors.toSet());

                    TaxonNodeDto parentDto = CdmStore.getService(ITaxonNodeService.class).findCommonParentDto(nodeDtos);

                    UUID taxonUuid = parentDto.getTaxonUuid();

                    int response = MessagingUtils.confirmDialog(

                            "Choose taxonomic scope",

                            String.format("The common parent taxon of this data set is :\n%s\n\n"

                                    + "Do you want to use this as the taxonomic scope for the polytomous key?"

                                    , parentDto.getTaxonTitleCache()), "Yes", "Choose different taxon", "Cancel");

                    if(response==2){

                    else if(response==1){

                        Taxon taxon = TaxonSelectionDialog.selectTaxon(getShell(), null);

                        if(taxon==null){

                            return;

                        }

                        taxonUuid = taxon.getUuid();

                    }

                    generateKey(matrix.getDescriptiveDataSet().getUuid(), taxonUuid);

            });

        }