Program: 190316
Project: 190316
Buggy source:
private synchronized void refreshModel(){
  refreshSelectedRankings();
  Ranking[] rankings=new Ranking[0];
  if (modelUI.getRanking() == RankingUIModel.NODE_RANKING) {
    rankings=model.getNodeRanking();
  }
 else {
    rankings=model.getEdgeRanking();
  }
  DefaultComboBoxModel comboBoxModel=new DefaultComboBoxModel();
  comboBoxModel.addElement(NO_SELECTION);
  comboBoxModel.setSelectedItem(NO_SELECTION);
  for (  Ranking r : rankings) {
    String elem=r.toString();
    comboBoxModel.addElement(elem);
    if (selectedRanking != null && selectedRanking.toString().equals(r.toString())) {
      comboBoxModel.setSelectedItem(elem);
    }
  }
  rankingComboBox.setModel(comboBoxModel);
  if (centerPanel != null) {
    remove(centerPanel);
  }
  applyButton.setVisible(false);
  splineButton.setVisible(false);
  if (selectedRanking != null) {
    Transformer transformer=getSelectedTransformer();
    TransformerUI transformerUI;
    if (transformer != null) {
      transformerUI=getUIForTransformer(transformer);
    }
 else {
      transformerUI=getUIForTransformer();
      if (transformerUI != null) {
        transformer=transformerUI.buildTransformer(selectedRanking);
        addTransformer(transformer);
      }
    }
    centerPanel=transformerUI.getPanel(transformer,selectedRanking);
    centerPanel.setBorder(BorderFactory.createCompoundBorder(BorderFactory.createEmptyBorder(5,5,0,5),BorderFactory.createEtchedBorder()));
    centerPanel.setOpaque(false);
    add(centerPanel,BorderLayout.CENTER);
    applyButton.setVisible(true);
    splineButton.setVisible(true);
  }
  revalidate();
  repaint();
}

Fixed version (ground truth):
public synchronized void refreshModel(){
  refreshSelectedRankings();
  Ranking[] rankings=new Ranking[0];
  if (modelUI.getRanking() == RankingUIModel.NODE_RANKING) {
    rankings=model.getNodeRanking();
  }
 else {
    rankings=model.getEdgeRanking();
  }
  DefaultComboBoxModel comboBoxModel=new DefaultComboBoxModel();
  comboBoxModel.addElement(NO_SELECTION);
  comboBoxModel.setSelectedItem(NO_SELECTION);
  for (  Ranking r : rankings) {
    String elem=r.toString();
    comboBoxModel.addElement(elem);
    if (selectedRanking != null && selectedRanking.toString().equals(r.toString())) {
      comboBoxModel.setSelectedItem(elem);
    }
  }
  rankingComboBox.setModel(comboBoxModel);
  if (centerPanel != null) {
    remove(centerPanel);
  }
  applyButton.setVisible(false);
  splineButton.setVisible(false);
  if (selectedRanking != null) {
    Transformer transformer=getSelectedTransformer();
    TransformerUI transformerUI;
    if (transformer != null) {
      transformerUI=getUIForTransformer(transformer);
    }
 else {
      transformerUI=getUIForTransformer();
      if (transformerUI != null) {
        transformer=transformerUI.buildTransformer(selectedRanking);
        addTransformer(transformer);
      }
    }
    centerPanel=transformerUI.getPanel(transformer,selectedRanking);
    centerPanel.setBorder(BorderFactory.createCompoundBorder(BorderFactory.createEmptyBorder(5,5,0,5),BorderFactory.createEtchedBorder()));
    centerPanel.setOpaque(false);
    add(centerPanel,BorderLayout.CENTER);
    applyButton.setVisible(true);
    splineButton.setVisible(true);
  }
  revalidate();
  repaint();
}