Java's collections framework has long needed a collection type that represents a sequence of elements with a defined encounter order and a uniform set of operations that apply across such collections.

The interfaces java.util.List and java.util.Set extend Collection, representing more specialized data structures and adding more operations and/or constraints.

The Set interface inherits its methods from Collection (java.util.Collection) and contains only those methods. In addition to sets, there are queues (java.util.Queue) and maps (java.util.Map).

Why should you use Collections class methods rather than similarly named fields to obtain empty collections? Type safety makes the crucial difference.