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how to combine the objects in arraylist based on the object's field

sheng zhong
Greenhorn

Joined: Nov 23, 2006
Posts: 20
For example, arraylist1 of arraylist2:

[[195.03, 500, MYC], [195.03, 200, MYC], [195.01, 200, MYC], [194.98, 400, MYC], [194.95, 600, NYC]]

I want to combine the first 2 arraylists since they have the same field one(195.03) and same field 3(MYC), and add the second field together(500+200). After combination the output is:

[[195.03, 700, MYC], [195.01, 200, MYC], [194.98, 400, MYC], [194.95, 600, NYC]]

Thanks!!!

[ May 01, 2008: Message edited by: sheng zhong ]
[ May 01, 2008: Message edited by: sheng zhong ]
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 38040
    
  22
Awkward.
I think you actually have a List of 4 objects, and you ought to get your elements into 4 objects. A List of Lists looks awkward to handle.

Then try sorting the List with Comparators for the 1st and last elements and iterate through the List with a for loop and combine pairs as appropriate.

It is likely there will be other ways to do it.
Anybody else got a better idea?
 
Consider Paul's rocket mass heater.
 
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