Menu
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?
785
HashMap does not maintains insertion order in java. Hashtable does not maintains insertion order in java. LinkedHashMap maintains insertion order in java. TreeMap is sorted by natural order of keys in java.
Duplicates: HashSet doesn't allow duplicate values. HashMap stores key, value pairs and it does not allow duplicate keys. If the key is duplicate then the old key is replaced with the new value.
This class extends HashMap and maintains a linked list of the entries in the map, in the order in which they were inserted. This allows insertion-order iteration over the map. That is, when iterating a LinkedHashMap, the elements will be returned in the order in which they were inserted.
Because Map's contract is that keys must be unique. So if you associate a new value to an existing key, it will override the value of the existing entry, not create a new entry: An object that maps keys to values. A map cannot contain duplicate keys; each key can map to at most one value.
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.
77
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
