Program: 8727
Project: 8727
Buggy source:
private static String parseFullTextExpression(FullTextExpression ft,final OakSolrConfiguration configuration){
  final StringBuilder fullTextString=new StringBuilder();
  ft.accept(new FullTextVisitor(){
    @Override public boolean visit(    FullTextOr or){
      fullTextString.append('(');
      for (int i=0; i < or.list.size(); i++) {
        FullTextExpression e=or.list.get(i);
        if (e.toString().equals("String_Node_Str")) {
          continue;
        }
        if (i > 0 && i < or.list.size()) {
          fullTextString.append("String_Node_Str");
        }
        String orTerm=parseFullTextExpression(e,configuration);
        fullTextString.append(orTerm);
      }
      fullTextString.append(')');
      fullTextString.append(' ');
      return true;
    }
    @Override public boolean visit(    FullTextContains contains){
      return contains.getBase().accept(this);
    }
    @Override public boolean visit(    FullTextAnd and){
      fullTextString.append('(');
      for (int i=0; i < and.list.size(); i++) {
        FullTextExpression e=and.list.get(i);
        if (e.toString().equals("String_Node_Str")) {
          continue;
        }
        if (i > 0 && i < and.list.size()) {
          fullTextString.append("String_Node_Str");
        }
        String andTerm=parseFullTextExpression(e,configuration);
        fullTextString.append(andTerm);
      }
      fullTextString.append(')');
      fullTextString.append(' ');
      return true;
    }
    @Override public boolean visit(    FullTextTerm term){
      if (term.isNot()) {
        fullTextString.append('-');
      }
      String p=term.getPropertyName();
      if (p != null && p.indexOf('/') >= 0) {
        p=getName(p);
      }
      if (p == null || "String_Node_Str".equals(p)) {
        p=configuration.getCatchAllField();
      }
      fullTextString.append(partialEscape(p));
      fullTextString.append(':');
      String termText=term.getText();
      if (termText.indexOf(' ') > 0) {
        fullTextString.append('"');
      }
      fullTextString.append(termText.replace("String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str"));
      if (termText.indexOf(' ') > 0) {
        fullTextString.append('"');
      }
      String boost=term.getBoost();
      if (boost != null) {
        fullTextString.append('^');
        fullTextString.append(boost);
      }
      fullTextString.append(' ');
      return true;
    }
  }
);
  return fullTextString.toString();
}

Fixed version (ground truth):
private static String parseFullTextExpression(FullTextExpression ft,final OakSolrConfiguration configuration){
  final StringBuilder fullTextString=new StringBuilder();
  ft.accept(new FullTextVisitor(){
    @Override public boolean visit(    FullTextOr or){
      fullTextString.append('(');
      for (int i=0; i < or.list.size(); i++) {
        FullTextExpression e=or.list.get(i);
        if (e.toString().contains("String_Node_Str")) {
          continue;
        }
        if (i > 0 && i < or.list.size()) {
          fullTextString.append("String_Node_Str");
        }
        String orTerm=parseFullTextExpression(e,configuration);
        fullTextString.append(orTerm);
      }
      fullTextString.append(')');
      fullTextString.append(' ');
      return true;
    }
    @Override public boolean visit(    FullTextContains contains){
      return contains.getBase().accept(this);
    }
    @Override public boolean visit(    FullTextAnd and){
      fullTextString.append('(');
      for (int i=0; i < and.list.size(); i++) {
        FullTextExpression e=and.list.get(i);
        if (e.toString().contains("String_Node_Str")) {
          continue;
        }
        if (i > 0 && i < and.list.size()) {
          fullTextString.append("String_Node_Str");
        }
        String andTerm=parseFullTextExpression(e,configuration);
        fullTextString.append(andTerm);
      }
      fullTextString.append(')');
      fullTextString.append(' ');
      return true;
    }
    @Override public boolean visit(    FullTextTerm term){
      if (term.isNot()) {
        fullTextString.append('-');
      }
      String p=term.getPropertyName();
      if (p != null && p.indexOf('/') >= 0) {
        p=getName(p);
      }
      if (p == null || "String_Node_Str".equals(p)) {
        p=configuration.getCatchAllField();
      }
      fullTextString.append(partialEscape(p));
      fullTextString.append(':');
      String termText=term.getText();
      if (termText.indexOf(' ') > 0) {
        fullTextString.append('"');
      }
      fullTextString.append(termText.replace("String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str"));
      if (termText.indexOf(' ') > 0) {
        fullTextString.append('"');
      }
      String boost=term.getBoost();
      if (boost != null) {
        fullTextString.append('^');
        fullTextString.append(boost);
      }
      fullTextString.append(' ');
      return true;
    }
  }
);
  return fullTextString.toString();
}