Flatten List and transform using closure

Groovy’s faltten method can be used to merge all the nested collections into one single collection. The level of nesting does not matter. We can also pass closure to perform any transformation.

def list = [[1,2,3], [4], [[5,6]]]

assert list.flatten() == [1, 2, 3, 4, 5, 6]

// Use closure to perform any transformations
assert list.flatten { it * 2 } == [2, 4, 6, 8, 10, 12]