Steps to reproduce: - create an array of CellRangeAddress objects, where at least two are direct neighbours. - call CellRangeUtil.mergeCellRanges(array) - You should see an UnsupportedOperationException thrown by AbstractList Analysis: The public method CellRangeUtil.mergeCellRanges() wraps an array into an ArrayList using Arrays.asList(...) to pass the result to the corresponding private method mergeCellRanges(). Under certain conditions mergeCellRanges() will try to shrink the list to a smaller size. The error occurs because structural modification of a wrapped Array is impossible. Problem: CellRangeUtil line 99, error occurs at line 124 Proposed solution: Copy the array into a list rather than creating a list view of the array.
Fixed in r892462, junit added. Your proposed solution is correct: the List in mergeCellRanges can be structurally modified and this method should copy the input array into the list, not use a list view of the input array. Thanks, Yegor