Program: 47106
Project: 47106
Buggy source:
private static boolean browseFolderForSubtitles(File subFolder,File file,DLNAMediaInfo media,final boolean useCache){
  boolean found=false;
  final Set<String> supported=SubtitleType.getSupportedFileExtensions();
  File[] allSubs=null;
  subtitleCacheLock.lock();
  try {
    if (useCache) {
      allSubs=subtitleCache.get(subFolder);
    }
    if (allSubs == null) {
      allSubs=subFolder.listFiles(new FilenameFilter(){
        @Override public boolean accept(        File dir,        String name){
          String ext=FilenameUtils.getExtension(name).toLowerCase();
          if ("String_Node_Str".equals(ext)) {
            return isFileExists(new File(dir,name),"String_Node_Str") == null;
          }
          return supported.contains(ext);
        }
      }
);
      if (allSubs != null) {
        subtitleCache.put(subFolder,allSubs);
      }
    }
  }
  finally {
    subtitleCacheLock.unlock();
  }
  String fileName=getFileNameWithoutExtension(file.getName()).toLowerCase();
  if (allSubs != null) {
    for (    File f : allSubs) {
      if (f.isFile() && !f.isHidden()) {
        String fName=f.getName().toLowerCase();
        for (        String ext : supported) {
          if (fName.length() > ext.length() && fName.startsWith(fileName) && endsWithIgnoreCase(fName,"String_Node_Str" + ext)) {
            int a=fileName.length();
            int b=fName.length() - ext.length() - 1;
            String code="String_Node_Str";
            if (a <= b) {
              code=fName.substring(a,b);
            }
            if (code.startsWith("String_Node_Str")) {
              code=code.substring(1);
            }
            boolean exists=false;
            if (media != null) {
              for (              DLNAMediaSubtitle sub : media.getSubtitleTracksList()) {
                if (f.equals(sub.getExternalFile())) {
                  exists=true;
                }
 else                 if (equalsIgnoreCase(ext,"String_Node_Str") && sub.getType() == SubtitleType.MICRODVD) {
                  sub.setType(SubtitleType.VOBSUB);
                  exists=true;
                }
 else                 if (equalsIgnoreCase(ext,"String_Node_Str") && sub.getType() == SubtitleType.VOBSUB) {
                  try {
                    sub.setExternalFile(f);
                  }
 catch (                  FileNotFoundException ex) {
                    LOGGER.warn("String_Node_Str",ex.getMessage());
                    LOGGER.trace("String_Node_Str",ex);
                  }
                  exists=true;
                }
              }
            }
            if (!exists) {
              DLNAMediaSubtitle sub=new DLNAMediaSubtitle();
              sub.setId(100 + (media == null ? 0 : media.getSubtitleTracksList().size()));
              if (code.length() == 0 || !Iso639.codeIsValid(code)) {
                sub.setLang(DLNAMediaSubtitle.UND);
                sub.setType(SubtitleType.valueOfFileExtension(ext));
                if (code.length() > 0) {
                  sub.setSubtitlesTrackTitleFromMetadata(code);
                  if (sub.getSubtitlesTrackTitleFromMetadata().contains("String_Node_Str")) {
                    String flavorLang=sub.getSubtitlesTrackTitleFromMetadata().substring(0,sub.getSubtitlesTrackTitleFromMetadata().indexOf('-'));
                    String flavorTitle=sub.getSubtitlesTrackTitleFromMetadata().substring(sub.getSubtitlesTrackTitleFromMetadata().indexOf('-') + 1);
                    if (Iso639.codeIsValid(flavorLang)) {
                      sub.setLang(flavorLang);
                      sub.setSubtitlesTrackTitleFromMetadata(flavorTitle);
                    }
                  }
                }
              }
 else {
                sub.setLang(code);
                sub.setType(SubtitleType.valueOfFileExtension(ext));
              }
              try {
                sub.setExternalFile(f);
              }
 catch (              FileNotFoundException ex) {
                LOGGER.warn("String_Node_Str",ex.getMessage());
                LOGGER.trace("String_Node_Str",ex);
              }
              found=true;
              if (media != null) {
                media.getSubtitleTracksList().add(sub);
              }
            }
          }
        }
      }
    }
  }
  return found;
}

Fixed version (ground truth):
private static boolean browseFolderForSubtitles(File subFolder,File file,DLNAMediaInfo media,final boolean useCache){
  boolean found=false;
  final Set<String> supported=SubtitleType.getSupportedFileExtensions();
  File[] allSubs=null;
  subtitleCacheLock.lock();
  try {
    if (useCache) {
      allSubs=subtitleCache.get(subFolder);
    }
    if (allSubs == null) {
      allSubs=subFolder.listFiles(new FilenameFilter(){
        @Override public boolean accept(        File dir,        String name){
          String ext=FilenameUtils.getExtension(name).toLowerCase();
          if ("String_Node_Str".equals(ext)) {
            return isFileExists(new File(dir,name),"String_Node_Str") == null;
          }
          return supported.contains(ext);
        }
      }
);
      if (allSubs != null) {
        subtitleCache.put(subFolder,allSubs);
      }
    }
  }
  finally {
    subtitleCacheLock.unlock();
  }
  String fileName=getFileNameWithoutExtension(file.getName()).toLowerCase();
  if (allSubs != null) {
    for (    File f : allSubs) {
      if (f.isFile() && !f.isHidden()) {
        String fName=f.getName().toLowerCase();
        for (        String ext : supported) {
          if (fName.length() > ext.length() && fName.startsWith(fileName) && endsWithIgnoreCase(fName,"String_Node_Str" + ext)) {
            int a=fileName.length();
            int b=fName.length() - ext.length() - 1;
            String code="String_Node_Str";
            if (a <= b) {
              code=fName.substring(a,b);
            }
            if (code.startsWith("String_Node_Str")) {
              code=code.substring(1);
            }
            boolean exists=false;
            if (media != null) {
              for (              DLNAMediaSubtitle sub : media.getSubtitleTracksList()) {
                if (f.equals(sub.getExternalFile())) {
                  exists=true;
                }
 else                 if (equalsIgnoreCase(ext,"String_Node_Str") && sub.getType() == SubtitleType.MICRODVD) {
                  sub.setType(SubtitleType.VOBSUB);
                  exists=true;
                }
 else                 if (equalsIgnoreCase(ext,"String_Node_Str") && sub.getType() == SubtitleType.VOBSUB) {
                  try {
                    sub.setExternalFile(f,null);
                  }
 catch (                  FileNotFoundException ex) {
                    LOGGER.warn("String_Node_Str",ex.getMessage());
                    LOGGER.trace("String_Node_Str",ex);
                  }
                  exists=true;
                }
              }
            }
            if (!exists) {
              String forcedLang=null;
              DLNAMediaSubtitle sub=new DLNAMediaSubtitle();
              sub.setId(100 + (media == null ? 0 : media.getSubtitleTracksList().size()));
              if (code.length() == 0 || !Iso639.codeIsValid(code)) {
                sub.setLang(DLNAMediaSubtitle.UND);
                sub.setType(SubtitleType.valueOfFileExtension(ext));
                if (code.length() > 0) {
                  sub.setSubtitlesTrackTitleFromMetadata(code);
                  if (sub.getSubtitlesTrackTitleFromMetadata().contains("String_Node_Str")) {
                    String flavorLang=sub.getSubtitlesTrackTitleFromMetadata().substring(0,sub.getSubtitlesTrackTitleFromMetadata().indexOf('-'));
                    String flavorTitle=sub.getSubtitlesTrackTitleFromMetadata().substring(sub.getSubtitlesTrackTitleFromMetadata().indexOf('-') + 1);
                    if (Iso639.codeIsValid(flavorLang)) {
                      sub.setLang(flavorLang);
                      sub.setSubtitlesTrackTitleFromMetadata(flavorTitle);
                      forcedLang=flavorLang;
                    }
                  }
                }
              }
 else {
                sub.setLang(code);
                sub.setType(SubtitleType.valueOfFileExtension(ext));
                forcedLang=code;
              }
              try {
                sub.setExternalFile(f,forcedLang);
              }
 catch (              FileNotFoundException ex) {
                LOGGER.warn("String_Node_Str",ex.getMessage());
                LOGGER.trace("String_Node_Str",ex);
              }
              found=true;
              if (media != null) {
                media.getSubtitleTracksList().add(sub);
              }
            }
          }
        }
      }
    }
  }
  return found;
}