The ST class represents an ordered symbol table of generic key-value pairs. It supports the usual put, get, contains, remove, size, and is-empty methods. equals(e2), and at most one null element. As implied by its name, this interface models the mathematical set abstraction. The Set interface places additional stipulations, beyond those inherited from the Collection interface, on. An interface in Java is a blueprint that defines a set of methods a class must implement without providing full implementation details. It helps achieve abstraction by focusing on what a class should do rather than how it does it.