Program: 5433
Project: 5433
Buggy source:
/** 
 * Constructs the query string of the announce request.
 * @param req Request to build the string from
 * @return The query string to send to the tracker
 */
protected static String getUrlParams(TrackerRequest req){
  try {
    StringBuilder sb=new StringBuilder("String_Node_Str");
    sb.append("String_Node_Str");
    sb.append(req.getInfoHash().toUrlEncodedString());
    sb.append("String_Node_Str");
    String peerstr=new String(req.getPeerId(),Charset.forName("String_Node_Str"));
    sb.append(URLEncoder.encode(peerstr,"String_Node_Str"));
    sb.append("String_Node_Str");
    sb.append(req.getPort());
    sb.append("String_Node_Str");
    sb.append(req.getBytesUploaded());
    sb.append("String_Node_Str");
    sb.append(req.getBytesDownloaded());
    sb.append("String_Node_Str");
    sb.append(req.getBytesLeft());
    if (req.isCompact() != null) {
      sb.append("String_Node_Str");
      sb.append(req.isCompact() ? "String_Node_Str" : "String_Node_Str");
    }
    sb.append("String_Node_Str");
    sb.append(req.getWantPeerId() ? "String_Node_Str" : "String_Node_Str");
    sb.append("String_Node_Str");
    sb.append(req.getEvent().getEventString());
    if (req.getIp() != null) {
      sb.append("String_Node_Str");
      sb.append(req.getIp().getHostAddress());
    }
    sb.append("String_Node_Str");
    sb.append(req.getNumWant());
    if (req.getKey() != null) {
      sb.append("String_Node_Str");
      sb.append(req.getKey());
    }
    if (req.getKey() != null) {
      sb.append("String_Node_Str");
      String trstr=new String(req.getTrackerId(),Charset.forName("String_Node_Str"));
      sb.append(URLEncoder.encode(trstr,"String_Node_Str"));
    }
    return sb.toString();
  }
 catch (  UnsupportedEncodingException e) {
    return null;
  }
}

Fixed version (ground truth):
/** 
 * Constructs the query string of the announce request.
 * @param req Request to build the string from
 * @return The query string to send to the tracker
 */
protected static String getUrlParams(TrackerRequest req){
  try {
    StringBuilder sb=new StringBuilder("String_Node_Str");
    sb.append("String_Node_Str");
    sb.append(req.getInfoHash().toUrlEncodedString());
    sb.append("String_Node_Str");
    String peerstr=new String(req.getPeerId(),Charset.forName("String_Node_Str"));
    sb.append(URLEncoder.encode(peerstr,"String_Node_Str"));
    sb.append("String_Node_Str");
    sb.append(req.getPort());
    sb.append("String_Node_Str");
    sb.append(req.getBytesUploaded());
    sb.append("String_Node_Str");
    sb.append(req.getBytesDownloaded());
    sb.append("String_Node_Str");
    sb.append(req.getBytesLeft());
    if (req.isCompact() != null) {
      sb.append("String_Node_Str");
      sb.append(req.isCompact() ? "String_Node_Str" : "String_Node_Str");
    }
    sb.append("String_Node_Str");
    sb.append(req.getWantPeerId() ? "String_Node_Str" : "String_Node_Str");
    sb.append("String_Node_Str");
    sb.append(req.getEvent().getEventString());
    if (req.getIp() != null) {
      sb.append("String_Node_Str");
      sb.append(req.getIp().getHostAddress());
    }
    sb.append("String_Node_Str");
    sb.append(req.getNumWant());
    if (req.getKey() != null) {
      sb.append("String_Node_Str");
      sb.append(req.getKey());
    }
    if (req.getTrackerId() != null) {
      sb.append("String_Node_Str");
      String trstr=new String(req.getTrackerId(),Charset.forName("String_Node_Str"));
      sb.append(URLEncoder.encode(trstr,"String_Node_Str"));
    }
    return sb.toString();
  }
 catch (  UnsupportedEncodingException e) {
    return null;
  }
}