elements of HashMap are in the wrong order [duplicate]

Answer 1

HashMap is not an ordered Collection. (It is not even a Collection) It is more like a dictionary.

If you want to perserve the order of the items you can either use a TreeMap or a LinkedHashMap.

The difference between these is that TreeMap keeps them ordered by their natural sort order while LinkedHashMap keeps the insertion order.

In most cases where you would like to have something like with using a List you can use the LinkedHashMap.

TreeMap uses a red-black tree for its internal implementation while LinkedHashMap uses doubly linked list.

My suggestion is that you should refer to the official documentation. There you will find thorough explanations.

Additionally the idiomatic way to iterate over Maps is this:

for(Integer key : map.keySet()) {
    String myString = map.get(key);
    // ...
}