lingochamp/FileDownloader · error · IllegalAccessException

invalid connection count

Error message

invalid connection count %d, the connection count must be larger than 0

What it means

Thrown by DownloadLaunchRunnable.run when the computed connection count for a multi-point (chunked) download is zero or negative. The connection count determines how many parallel range connections split the file; a non-positive value means the model/total-length inspection produced an invalid chunk plan, so the download cannot proceed and is failed with an IllegalArgumentException-style assertion.

Solutions

  1. Ensure the download is created with a valid connection count (FileDownloadHelper config) larger than 0 when using multi-point download.
  2. Check that the task model and its resumed state in the database are not corrupted (inspect ConnectionModel rows for the task id).
  3. Retry the download after clearing its persisted state so the connection plan is recomputed from scratch.
  4. Catch the error in the download listener's error callback and restart the task with default single-connection settings.
Defensive patterns

Strategy: validation

When it happens

Trigger: Thrown at library/src/main/java/com/liulishuo/filedownloader/download/DownloadLaunchRunnable.java:277 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of lingochamp/FileDownloader@6237a8cac1 (2026-09-08). Data as JSON: /api/errors/e24ed568552cfae6. Report an issue: GitHub.

Appendix: source

Thrown at library/src/main/java/com/liulishuo/filedownloader/download/DownloadLaunchRunnable.java:277

                    // 4. check local resume model
                    final List<ConnectionModel> connectionOnDBList = database
                            .findConnectionModel(model.getId());
                    inspectTaskModelResumeAvailableOnDB(connectionOnDBList);

                    if (paused) {
                        model.setStatus(FileDownloadStatus.paused);
                        return;
                    }

                    final long totalLength = model.getTotal();

                    // 5. pre-allocate if need.
                    handlePreAllocate(totalLength, model.getTempFilePath());

                    // 6. calculate block count
                    final int connectionCount = calcConnectionCount(totalLength);
                    if (connectionCount <= 0) {
                        throw new IllegalAccessException(FileDownloadUtils
                                .formatString("invalid connection count %d, the connection count"
                                        + " must be larger than 0", connectionCount));
                    }

                    if (totalLength == 0) {
                        return;
                    }

                    if (paused) {
                        model.setStatus(FileDownloadStatus.paused);
                        return;
                    }

                    // 7. start real connect and fetch to local filesystem
                    isSingleConnection = connectionCount == 1;
                    if (isSingleConnection) {
                        // single connection
                        realDownloadWithSingleConnection(totalLength);

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