As the title says is there a simple way to change the key of my hashmap?
Here I update all the values of my hashmap
stock.put(itemCode.getText(), new StockData.Item(itemName.getText(),(Double) priceS.getValue(), (Integer)quantityS.getValue(), file.getName())); and now I would like to change the key, I used earlier removing and inserting data that worked but the order was changed which I don't want to happen.
If you want to use a HashMap, your keys should never change after insertion.
If the order matters to you, you should be using an implementation of a SortedMap (e.g. TreeMap) instead.
I don't think you can. A HashMap has no order, objects are inserted based on the hash value of the key, if you change the key, you change its hash and thus the bucket it appears in inside the HashMap. If you want to order the map you are better off using a TreeMap
We hit this problem moving from Java 7 to Java 8 several tests asserted the contents of a HashMap based on the HashMaps toString value, this has no determined order, but under Java 7 it seemed to work but the tests failed under Java 8.
LinkedHashMap - depends what the OP want.HashMap based on the HashMaps toString value". Ooops...
HashMap doesn't guarantee the order of the items, their location inside the HashMap is determined by the hashcode which is calculated from the key. Therefor changing the key will change the location, as you actually removing the previous key value entry and inserting a new entry.
From HashMap 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.
HashMaphas no order. What do you mean by "the order was changed"?