The collection classes are used to manipulate collections of objects. A collection is an object that contains a number of items, which can be any objects. These manipulations might include counting objects, organizing them, or assigning them a supplier (for example, to indicate that a specific assortment of baked goods is supplied by the Pie-by-Night Bakery).
Rexx includes classes, for example, for arrays, lists, queues, tables, and directories. Each item stored in a Rexx collection has an associated index that you can use to retrieve the item from the collection with the AT or [] (left and right bracket) methods, and each collection defines its own acceptable index types:
The class Collection is a mixin class (it can be inherited by other classes), it subclasses (specializes) The Object Class .