日期格式

为什么无法改变日期格式

相关代码：

DateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH-mm-sss");
List<Category> newList = new ArrayList<>();
for (Category category : categoryList) {
    Date date = null;
    try {
        String string = sdf.format(category.getCreateTime());
        date = sdf.parse("2018-09-07 12-08-000");
        System.out.println(string);
        System.out.println(date);
    } catch (ParseException e) {
        e.printStackTrace();
    }
    if (date != null) {
        category.setCreateTime(date);
    }
    newList.add(category);
}
System.out.println(newList);