Groovy Goodness: Collate a List into Sub-lists
Join the DZone community and get the full member experience.Join For Free
I totally missed the new collate() method for List objects available since Groovy 1.8.6. With this method we can divide a list into sub-lists of a specified size. We can include a boolean parameter to indicate if we want to include remainders that don't fit in the specified size of the collated sub-lists. Finally we can use a parameter to define how many steps we go through the list before dividing the list into sub-lists.
def letters = 'a'..'g' assert letters.collate(3) == [['a', 'b', 'c'], ['d', 'e', 'f'], ['g']] // Step through original list with // 2 steps and collate. assert letters.collate(3, 2) == [['a', 'b', 'c'], ['c', 'd', 'e'], ['e', 'f', 'g'], ['g']] // Don't include remainder in result. // Default a remainder is included in the result. boolean remainder = false assert letters.collate(3, remainder) == [['a', 'b', 'c'], ['d', 'e', 'f']] assert letters.collate(3, 2, remainder) == [['a', 'b', 'c'], ['c', 'd', 'e'], ['e', 'f', 'g']]
Published at DZone with permission of Hubert Klein Ikkink, DZone MVB. See the original article here.
Opinions expressed by DZone contributors are their own.