In a previous post, we learned about the
intersect method being added to collections in Groovy. Since Groovy 2.5.0, we can supply a custom
Comparator to the
intersect method to define our own rules for the intersection.
In the following example, we first apply the
intersect method with the default
Comparator. Then we create a new
Comparator using a closure where we check if the value is in both collections and if the value starts with the letter M: