[Demonstration 1]

[Buggy Method]
@Override
public void doAjax(StaplerRequest req, StaplerResponse rsp, @Header("n") String n) throws IOException, ServletException {
    if (n == null) {
        throw HttpResponses.error(SC_BAD_REQUEST, new IllegalArgumentException("Missing the 'n' HTTP header"));
    }
    rsp.setContentType("text/html;charset=UTF-8");
    List<T> items = new LinkedList<T>();
    String nn = null;
    Iterable<T> builds = model.getBuildsAfter(n);
    for (T t : builds) {
        if (adapter.compare(t, n) >= 0) {
            items.add(t);
            if (adapter.isBuilding(t)) {
                nn = adapter.getKey(t);
            }
        } else {
            break;
        }
    }
    if (nn == null) {
        if (items.isEmpty()) {
            nn = n;
        } else {
            nn = adapter.getNextKey(adapter.getKey(items.get(0)));
        }
    }
    baseList = items;
    GReflectionUtils.setField(HistoryWidget.class, "firstTransientBuildKey", this, nn);
    rsp.setHeader("n", nn);
    req.getView(this, "ajaxBuildHistory.jelly").forward(req, rsp);
}

[Buggy Hunk]
Iterable<T> builds = model.getBuildsAfter(n);

[Patch]
Iterable<T> builds =  model.getBuildsAfter(Integer.parseInt(n));

[Demonstration 2]

[Buggy Method]
private static <C extends CodeEnum<C>> Stream<C> enums(Class<C> code) {
    if (code.isEnum()) {
        return Stream.of(code.getEnumConstants());
    }
    throw new IllegalArgumentException("CodeEnum must be enum. class=[" + code + "].");
}

[Buggy Hunk]
throw new IllegalArgumentException("CodeEnum must be enum. class=[" + code + "].");

[Patch]
throw new IllegalArgumentException(String.format("CodeEnum must be enum. class=[%s].", code.getName()));

[Demonstration 3]

[Buggy Method]
public static Result service(String ownerName, String projectName, String service, boolean isAdvertise) throws IOException, UnsupportedOperationException, ServletException {
    if (!isSupportedService(service)) {
        return forbidden(String.format("Unsupported service: '%s'", service));
    }
    Project project = Project.findByOwnerAndProjectName(ownerName, projectName);
    if (project == null) {
        return notFound();
    }
    models.User user = UserApp.currentUser();
    if (!isAllowed(project, service)) {
        if (user.isAnonymous()) {
            return BasicAuthAction.unauthorized(response());
        } else {
            // If you want the Git client showing your custom message to
            // the user, the Content-Type should be exact "text/plain"
            // without any parameter. For more details, see the code at
            // https://github.com/git/git/commit/426e70d4a11ce3b4f70636d57c6a0ab16ae08a00#diff-eea0ad565ec5903a11b6023755d491cfR154
            response().setHeader("Content-Type", "text/plain");
            return forbidden(String.format("'%s' has no permission to '%s/%s'.", user.name, ownerName, projectName));
        }
    }
    if (isAdvertise) {
        return ok(RepositoryService.gitAdvertise(project, service, response()));
    } else {
        if (request().body().isMaxSizeExceeded()) {
            return status(REQUEST_ENTITY_TOO_LARGE);
        } else {
            user.visits(project);
            return ok(RepositoryService.gitRpc(project, service, request(), response()));
        }
    }
}

[Buggy Hunk]
user.name, ownerName, projectName));

[Patch]
user.loginId, ownerName, projectName));