[Demonstration 1]

[Buggy Method]
@Override
public List<String> buildNGrams(String text) {
    List<String> list = new LinkedList<>();
    CircularCharBuffer buffer = new CircularCharBuffer(ngramSize);
    char[] array = text.toLowerCase().toCharArray();
    for (char cc : array) {
        char c = cc;
        if (Character.isDigit(c)) {
            continue;
        } else if (isPunctuation(c)) {
            c = ' ';
        }
        if (Character.isWhitespace(c)) {
            if (buffer.isEmpty()) {
                buffer.append(' ');
            } else {
                char lastchar = buffer.peekHead();
                if (lastchar == ' ') {
                    if (buffer.length() == ngramSize) {
                        list.add(buffer.toString());
                    }
                    buffer.clear();
                    buffer.append(' ');
                } else {
                    buffer.append(' ');
                    if (buffer.length() == ngramSize) {
                        list.add(buffer.toString());
                        buffer.clear();
                    } else {
                        buffer.clear();
                        buffer.append(' ');
                    }
                }
            }
        } else {
            if (buffer.isEmpty()) {
                buffer.append(' ');
            }
            char lastchar = buffer.peekHead();
            if (lastchar == ' ' && buffer.length() > 1) {
                buffer.clear();
                buffer.append(' ');
            }
            buffer.append(c);
            if (buffer.length() == ngramSize) {
                list.add(buffer.toString());
            }
        }
    }
    return list;
}

[Buggy Hunk]
} else if (isPunctuation(c)) {

[Patch]
} else if (CharUtils.isPunctuation(c)) {

[Demonstration 2]

[Buggy Method]
public String arrayToString(Object[] array) {
    StringBuffer buffer = new StringBuffer();
    for (int i = 0; i < array.length; i++) {
        if (i > 0) {
            buffer.append(arraySeparator);
        }
        buffer.append(objectToString(array[i]));
    }
    return buffer.toString();
}

[Buggy Hunk]
StringBuffer buffer = new StringBuffer();

[Patch]
StringBuilder buffer = new StringBuilder();

[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));