void rollOver()

in src/main/java/org/apache/log4j/RollingFileAppender.java [127:201]
54 lines of code
14 McCabe index (conditional complexity)

  void rollOver() {
    File target;
    File file;

    if (qw != null) {
        long size = ((CountingQuietWriter) qw).getCount();
        LogLog.debug("rolling over count=" + size);
        //   if operation fails, do not roll again until
        //      maxFileSize more bytes are written
        nextRollover = size + maxFileSize;
    }
    LogLog.debug("maxBackupIndex="+maxBackupIndex);

    boolean renameSucceeded = true;
    // If maxBackups <= 0, then there is no file renaming to be done.
    if(maxBackupIndex > 0) {
      // Delete the oldest file, to keep Windows happy.
      file = new File(fileName + '.' + maxBackupIndex);
      if (file.exists())
       renameSucceeded = file.delete();

      // Map {(maxBackupIndex - 1), ..., 2, 1} to {maxBackupIndex, ..., 3, 2}
      for (int i = maxBackupIndex - 1; i >= 1 && renameSucceeded; i--) {
	file = new File(fileName + "." + i);
	if (file.exists()) {
	  target = new File(fileName + '.' + (i + 1));
	  LogLog.debug("Renaming file " + file + " to " + target);
	  renameSucceeded = file.renameTo(target);
	}
      }

    if(renameSucceeded) {
      // Rename fileName to fileName.1
      target = new File(fileName + "." + 1);

      this.closeFile(); // keep windows happy.

      file = new File(fileName);
      LogLog.debug("Renaming file " + file + " to " + target);
      renameSucceeded = file.renameTo(target);
      //
      //   if file rename failed, reopen file with append = true
      //
      if (!renameSucceeded) {
          try {
            this.setFile(fileName, true, bufferedIO, bufferSize);
          }
          catch(IOException e) {
              if (e instanceof InterruptedIOException) {
                  Thread.currentThread().interrupt();
              }
              LogLog.error("setFile("+fileName+", true) call failed.", e);
          }
      }
    }
    }

    //
    //   if all renames were successful, then
    //
    if (renameSucceeded) {
    try {
      // This will also close the file. This is OK since multiple
      // close operations are safe.
      this.setFile(fileName, false, bufferedIO, bufferSize);
      nextRollover = 0;
    }
    catch(IOException e) {
        if (e instanceof InterruptedIOException) {
            Thread.currentThread().interrupt();
        }
        LogLog.error("setFile("+fileName+", false) call failed.", e);
    }
    }
  }