Program: 16876
Project: 16876
Buggy source:
public void parse(BufferedReader buf) throws IOException {
  triggerDocumentStart();
  struct=new Struct();
  String line=null;
  boolean inLoop=false;
  List<String> loopFields=new ArrayList<String>();
  List<String> lineData=new ArrayList<String>();
  Set<String> loopWarnings=new HashSet<String>();
  String category=null;
  line=buf.readLine();
  if (!line.startsWith("String_Node_Str")) {
    logger.error("String_Node_Str" + line);
    triggerDocumentEnd();
    return;
  }
  while ((line=buf.readLine()) != null) {
    if (inLoop) {
      if (line.startsWith(LOOP_END)) {
        inLoop=false;
        lineData.clear();
        category=null;
        loopFields.clear();
        loopWarnings.clear();
        continue;
      }
      if (line.startsWith(FIELD_LINE)) {
        String txt=line.trim();
        if (txt.indexOf('.') > -1) {
          String[] spl=txt.split("String_Node_Str");
          category=spl[0];
          String attribute=spl[1];
          loopFields.add(attribute);
          if (spl.length > 2) {
            logger.warn("String_Node_Str");
          }
        }
 else {
          category=txt;
        }
      }
 else {
        lineData=processLine(line,buf,loopFields.size());
        if (lineData.size() != loopFields.size()) {
          logger.warn("String_Node_Str");
        }
        endLineChecks(category,loopFields,lineData,loopWarnings);
        lineData.clear();
      }
    }
 else {
      if (line.startsWith(LOOP_START)) {
        loopFields.clear();
        loopWarnings.clear();
        inLoop=true;
        category=null;
        lineData.clear();
        continue;
      }
 else       if (line.startsWith(LOOP_END)) {
        inLoop=false;
        if (category != null)         endLineChecks(category,loopFields,lineData,loopWarnings);
        category=null;
        loopFields.clear();
        loopWarnings.clear();
        lineData.clear();
      }
 else {
        List<String> data=processLine(line,buf,2);
        if (data.size() < 1) {
          lineData.clear();
          continue;
        }
        String key=data.get(0);
        int pos=key.indexOf("String_Node_Str");
        if (pos < 0) {
          if (!line.startsWith("String_Node_Str")) {
            logger.warn("String_Node_Str" + line);
            triggerDocumentEnd();
            return;
          }
          category=null;
          lineData.clear();
          continue;
        }
        category=key.substring(0,pos);
        String value=data.get(1);
        loopFields.add(key.substring(pos + 1,key.length()));
        lineData.add(value);
      }
    }
  }
  if (struct != null) {
    triggerStructData(struct);
  }
  triggerDocumentEnd();
}

Fixed version (ground truth):
public void parse(BufferedReader buf) throws IOException {
  triggerDocumentStart();
  struct=new Struct();
  String line=null;
  boolean inLoop=false;
  List<String> loopFields=new ArrayList<String>();
  List<String> lineData=new ArrayList<String>();
  Set<String> loopWarnings=new HashSet<String>();
  String category=null;
  line=buf.readLine();
  if (!line.startsWith("String_Node_Str")) {
    logger.error("String_Node_Str" + line);
    triggerDocumentEnd();
    return;
  }
  while ((line=buf.readLine()) != null) {
    logger.debug(inLoop + "String_Node_Str" + line);
    if (inLoop) {
      if (line.startsWith(LOOP_END)) {
        inLoop=false;
        lineData.clear();
        category=null;
        loopFields.clear();
        loopWarnings.clear();
        continue;
      }
      if (line.startsWith(FIELD_LINE)) {
        String txt=line.trim();
        if (txt.indexOf('.') > -1) {
          String[] spl=txt.split("String_Node_Str");
          category=spl[0];
          String attribute=spl[1];
          loopFields.add(attribute);
          if (spl.length > 2) {
            logger.warn("String_Node_Str");
          }
        }
 else {
          category=txt;
        }
      }
 else {
        lineData=processLine(line,buf,loopFields.size());
        if (lineData.size() != loopFields.size()) {
          logger.warn("String_Node_Str");
        }
        endLineChecks(category,loopFields,lineData,loopWarnings);
        lineData.clear();
      }
    }
 else {
      if (line.startsWith(LOOP_START)) {
        loopFields.clear();
        loopWarnings.clear();
        inLoop=true;
        category=null;
        lineData.clear();
        continue;
      }
 else       if (line.startsWith(LOOP_END)) {
        inLoop=false;
        if (category != null)         endLineChecks(category,loopFields,lineData,loopWarnings);
        category=null;
        loopFields.clear();
        loopWarnings.clear();
        lineData.clear();
      }
 else {
        List<String> data=processLine(line,buf,2);
        if (data.size() < 1) {
          lineData.clear();
          continue;
        }
        String key=data.get(0);
        int pos=key.indexOf("String_Node_Str");
        if (pos < 0) {
          if (!line.startsWith("String_Node_Str")) {
            logger.warn("String_Node_Str" + line);
            triggerDocumentEnd();
            return;
          }
          category=null;
          lineData.clear();
          continue;
        }
        category=key.substring(0,pos);
        String value=data.get(1);
        loopFields.add(key.substring(pos + 1,key.length()));
        lineData.add(value);
      }
    }
  }
  if (struct != null) {
    triggerStructData(struct);
  }
  triggerDocumentEnd();
}