List<String> getOrder = dataSave.getDataList("orderList");
            ArrayList<String> newOrderList = new ArrayList<>();
            //存在则添加新的到第一个位置
            if (getOrder != null && getOrder.size() > 0) {
                newOrderList.addAll(getOrder);
                if (!isExitOrderData(getOrder, orderId)) {
                    newOrderList.add(0, orderId);
                }
            } else {
            //不存在则直接添加
                newOrderList.add(orderId);
            }
            dataSave.setDataList("orderList", newOrderList);
             //去重
            ArrayList<String> idList = removeDuplicate(newOrderList);
 

String转List<String>工具类

/**
 * create by AMOS
 * on 2021/11/12
 * explain${String转List工具类}
 */
public class ListDataSave {
    private SharedPreferences preferences;
    private SharedPreferences.Editor editor;

    public ListDataSave(Context mContext, String preferenceName) {
        preferences = mContext.getSharedPreferences(preferenceName, Context.MODE_PRIVATE);
        editor = preferences.edit();
    }

    /**
     * 保存List
     *
     * @param tag
     * @param datalist
     */
    public <T> void setDataList(String tag, List<T> datalist) {
        if (null == datalist || datalist.size() <= 0) {
            return;
        }
        Gson gson = new Gson();
        //转换成json数据，再保存
        String strJson = gson.toJson(datalist);
        editor.clear();
        editor.putString(tag, strJson);
        editor.commit();
    }

    /**
     * 获取List
     *
     * @param tag
     * @return
     */
    public <T> List<T> getDataList(String tag) {
        List<T> datalist = new ArrayList<T>();
        String strJson = preferences.getString(tag, null);
        if (null == strJson) {
            return datalist;
        }
        Gson gson = new Gson();
        datalist = gson.fromJson(strJson, new TypeToken<List<T>>() {
        }.getType());
        return datalist;
    }
}

List<String去重

    // 列表去重
    private ArrayList<String> removeDuplicate(ArrayList<String> list) {
        LinkedHashSet set = new LinkedHashSet(list);
        list.clear();
        list.addAll(set);
        return list;
    }

    // 是否存在ID相同, 存在返回true, 不存在則返回false
    private boolean isExitOrderData(List<String> oldData, String newOrder) {
        boolean isExitHistoryData = false;
        for (String historyBean : oldData) {
            if (TextUtils.equals(historyBean, newOrder)) {
                isExitHistoryData = true;
                break;
            }
        }
        return isExitHistoryData;
    }