#fixed code
                              protected void commitFiles(File sourceRoot, String destinationRoot) throws IOException {
    File[] files = sourceRoot.listFiles();
    if (files == null) {
      throw new IOException("Failed to commit files from " + sourceRoot + " to " + destinationRoot + " since source is not a valid directory.");
    }
    for (File file : files) {
      // Skip non files
      if (!file.isFile()) {
        continue;
      }
      File targetFile = new File(destinationRoot + "/" + file.getName());
      // If target file already exists, delete it
      if (targetFile.exists()) {
        if (!targetFile.delete()) {
          throw new IOException("Failed to overwrite file in destination root: " + targetFile.getAbsolutePath());
        }
      }
      // Move file to destination
      if (!file.renameTo(targetFile)) {
        LOG.info("Committing " + file.getAbsolutePath() + " to " + targetFile.getAbsolutePath());
        throw new IOException("Failed to rename source file: " + file.getAbsolutePath()
            + " to destination file: " + targetFile.getAbsolutePath());
      }
    }
  }
#vulnerable code 
                              protected void commitFiles(File sourceRoot, String destinationRoot) throws IOException {
    for (File file : sourceRoot.listFiles()) {
      // Skip non files
      if (!file.isFile()) {
        continue;
      }
      File targetFile = new File(destinationRoot + "/" + file.getName());
      // If target file already exists, delete it
      if (targetFile.exists()) {
        if (!targetFile.delete()) {
          throw new IOException("Failed to overwrite file in destination root: " + targetFile.getAbsolutePath());
        }
      }
      // Move file to destination
      if (!file.renameTo(targetFile)) {
        LOG.info("Committing " + file.getAbsolutePath() + " to " + targetFile.getAbsolutePath());
        throw new IOException("Failed to rename source file: " + file.getAbsolutePath()
            + " to destination file: " + targetFile.getAbsolutePath());
      }
    }
  } 
                            #location 2 
                            #vulnerability type NULL_DEREFERENCE