Groovy Goodness: Transform Elements While Flattening [Snippet]

We can use the flatten method in Groovy to flatten a collection that contains other collections into a single collection with all elements. We can pass a closure as an extra argument to the flatten method to transform each element that is flattened. The argument of the closure is the element from the original collection.

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In the following example, we first use the flatten method without a closure argument. Then we pass a closure argument and transform the element:

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

// Simple flatten the nested collections.

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

// We can use a closure to transform

// the elements in the resulting collection.

assert list.flatten { it * 2 } == [2, 4, 6, 8]

Written with Groovy 2.5.7.

Further Reading

[DZone Refcard] Getting Started With Groovy

Statically Compiled Groovy: Give Groovy a Chance