Merge two ArrayList in java

Question

I have two identical array lists in java each having a string value and an integer count. Now I have to merge these array lists into a single one, in which if the value is present, i will just increment the count, if the value is not present, i will just add the value and the count as such.

The question is, is there anyway I can do it graciously other than iterating in a for loop and if checking every value?

could you give some example input/output pairs? your question is a little vague, and that could clear it up a bit — mfsiega
– mfsiega, Commented Apr 12, 2012 at 5:44
@RangiLin the problem is i get the arraylist from another system over which I don't have control :( — Greenhorn
– Greenhorn, Commented Apr 12, 2012 at 5:47

Bozho · Accepted Answer · 2012-04-12 05:46:23Z

3

You can't, there's too much custom logic. Iterate, check and add - that's the best approach, and will be more readable.

Technically, you can use a Multiset from guava, but there the count is taken care of by the collection itself, rather than you, so it might require some more work.

answered Apr 12, 2012 at 5:46

Bozho

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stacker · Accepted Answer · 2012-04-12 05:49:00Z

1

The question is, is there anyway I can do it graciously other than iterating in a for loop and if checking every value?

Short answer is no.

You would be better of using HashMap as a container, at least the merging operation would perform faster. You need a loop in any case. (since there is no addAll / putAll wich could update your counts).

answered Apr 12, 2012 at 5:49

stacker

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