Java 哈希映射键奇怪的键顺序

我正在做一个HashMap，它使用日期作为键，并为他们分配一个宠物服从对象(每月的宠物).宠物有一堆价值观，比如名字、年龄、类型……(不相关)，并且有一个随机生成一个的方法.事情大概是这样的:

DateTimeFormatter date_format = DateTimeFormatter.ofPattern ("dd/MM/yyyy");
LocalDate date = LocalDate.of(2023, 1, 1);
HashMap<LocalDate, Pet> pets = new HashMap<>();

//* This next chunk generates a random pet (that has not yet been chosen) and makes it the pet of the month using the date as the key and the pet as the value

for (int i=0; i < 12; i++){
            Pet pet_of_the_month = Pet.randompet(); 
            if (!pets.containsValue(pet_of_the_month)){ 
                pets.put(date, pet_of_the_month); 
                date = date.plusMonths(1);
            } else {
                i--;
            }
        }

//*This loops around the map taking every key and printing both the key (date) and the object (pet)

for (LocalDate month: pets.keySet()) {
            System.out.println("Date of" + month.format(date.format) + ":" + pets.get(month).toString());
        }

我的问题是，由于某种原因，它总是先打印月份4，然后按顺序打印其余月份(4，1，2，3，5，6...)；它这样做有什么原因吗？我是做错了什么/错过了什么，还是我必须假设的某种随机交互？