How to preserve insertion order in HashMap? [duplicate]

I'm using a HashMap. When I iterate over the map, the data is returned in (often the same) random order. But the data was inserted in a specific order, and I need to preserve the insertion order. How can I do this?

Solution 1:

LinkedHashMap is precisely what you're looking for.

It is exactly like HashMap, except that when you iterate over it, it presents the items in the insertion order.

Solution 2:

HashMap is unordered per the second line of the documentation:

This class makes no guarantees as to the order of the map; in particular, it does not guarantee that the order will remain constant over time.

Perhaps you can do as aix suggests and use a LinkedHashMap, or another ordered collection. Take a look on javapractices.com's guide on Choosing the right Collection.