Groovy 5 introduced some extra overloaded methods for the collectEntries method, that can be used to transform an iterable object into a Map. You can now pass a closure or function as arguments to transform the original iterable element into the key and value for the resulting Map. It is now also possible to pass a so-called collector Map that will be used to extend with new key/value pairs.

Besides extra overloaded method signatures for collectEntries Groovy 5 also adds the new methods withCollectedKeys and withCollectedValues. With the method withCollectedKeys a closure or function can passed to create the keys for the new Map based on the elements from the iterable. The value of the key/value pair is the unchanged element. You use the method withCollectedValues to pass a closure or function to create the value for the new key/value pair in the resulting Map. The key will be the original element from the iterable.