[Demonstration 1]

[Buggy Method]
public void hintButton(ActionEvent actionEvent) {
    Random rn = new Random();
    ArrayList<Button> buttons = new ArrayList<>();
    buttons.add(firstButton);
    buttons.add(secondButton);
    buttons.add(thirdButton);
    buttons.add(firstButton);
    Question question = questions.get(Question.getQuestionIndex());
    buttons = question.jokerBtn(buttons);
    for (int i = 0; i < 2; i++) {
        int index = rn.nextInt(buttons.size());
        buttons.get(index).setDisable(true);
        buttons.remove(index);
    }
    hintOne.setDisable(true);
}

[Buggy Hunk]
buttons.add(firstButton);

[Patch]
buttons.add(fourthButton);

[Demonstration 2]

[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));

[Demonstration 3]

[Buggy Method]
public void onCommand(CommandSender cs, String[] args) {
    if (args.length == 1) {
        if (!(cs instanceof Player)) {
            cs.sendMessage(Lang.TITLE.toString() + Lang.NOT_PLAYER.toString());
            return;
        }
        final Player p = (Player) cs;
        p.getInventory().addItem(CSkull.getPlayerSkull(args[0]));
        p.sendMessage(Lang.TITLE.toString() + Lang.PLAYER_HEAD_RECEIVED.toString().replace("%r", "You").replace("%p", args[0]));
    } else if (args.length == 2) {
        if (!cs.hasPermission("headdrop.head.other")) {
            cs.sendMessage(Lang.TITLE.toString() + Lang.NO_PERMISSION.toString());
            return;
        }
        @SuppressWarnings("deprecation")
        final Player target = Bukkit.getPlayer(args[0]);
        if (target == null) {
            cs.sendMessage(Lang.TITLE.toString() + Lang.NOT_ONLINE.toString());
        } else {
            target.getInventory().addItem(CSkull.getPlayerSkull(args[1]));
            cs.sendMessage(Lang.TITLE.toString() + Lang.PLAYER_HEAD_RECEIVED.toString().replace("%r", target.getName()).replace("%p", args[0]));
        }
    }
}

[Buggy Hunk]
cs.sendMessage(Lang.TITLE.toString() + Lang.PLAYER_HEAD_RECEIVED.toString().replace("%r", target.getName()).replace("%p", args[0]));

[Patch]
cs.sendMessage(Lang.TITLE.toString() + Lang.PLAYER_HEAD_RECEIVED.toString().replace("%r", target.getName()).replace("%p", args[1]));