CODEWITHSUNDEEP
java
Maksim
Maksim

Reputation: 16931

Swap/Reorder records

I have records in the database with the sort order number. Now I want to create a UI with buttons UP and DOWN to reorder them. What is the best algorithm to make two functionsUp(record) and functionDown(record) in order to rearrange them by changing orderNum and them persist that number to the database.

Here is the example of what I'm trying to achieve (before foo=24, after foo=25):

Before pressing up on bar

id | name | orderNum
-------------------- 
1  | foo  | 24
2  | bar  | 25
3  | doe  | 26

After

id | name | orderNum
-------------------- 
1  | foo  | 25
2  | bar  | 24
3  | doe  | 26

Upvotes: 0

Views: 145

Answers (3)

Mr. Will
Mr. Will

Reputation: 2308

If you are wanting to sort them on the UI, you should map each record in your ResultSet to a bean. Then you can have your bean implement the Comparable interface and use that to sort your collection.

If you want to sort on different fields, depending on which is selected you can also write Comparators for each of the fields and inject the Comparator for the selected column at runtime.

Upvotes: 0

user800014
user800014

Reputation:

Assuming that you are using Java Collections, you can write a class that implements Comparable and use the utility Collections.sort(). More info about ordering colletions here.

Upvotes: 1

kamil
kamil

Reputation: 3522

Assuming he doesn't want ask for the data from database again nd again, just to sort data he selected, why not quick sort algorithm?

Of course if I'm right. If not, just follow @ggrigery solution

Upvotes: 0

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