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Asked: 2026-05-24T13:55:39+00:00

I have a TreeBasedTable object from Guava (Gooogle Collections). It is in the form

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I have a TreeBasedTable object from Guava (Gooogle Collections). It is in the form of TreeBasedTable<k1, k2, v>. k1 and k2 implement Comparable. Now when I display the table, I want the user to be able to sort it different ways to change the order of the values.

The approach I tried was to iterate over the table, and for each value, change a variable that’s used in the Compare method. The trouble is it gets through the loop once, and then returns a NullPointerException, which I think I’ve narrowed down to trying to change the order whilst iterating over it (rookie mistake, I know).

So I was wondering, what would be a good way to reorder this table?

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1 Answer

  1. Editorial Team

    How about if you just create a new TreeBasedTable, created with a different comparator object, and then copy the original into it via public putAll method? The put for each element will take log(N), so total time should be N log(n), which is about the time I would expect for a re-sort to take.

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