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Interfaces
The Collection Interface
The Set Interface
The List Interface
The Queue Interface
The Deque Interface
The Map Interface
Object Ordering
The SortedSet Interface
The SortedMap Interface
Summary of Interfaces
Questions and Exercises
Trail: Collections
Lesson: Interfaces
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# Summary of Interfaces

The core collection interfaces are the foundation of the Java Collections Framework.

The Java Collections Framework hierarchy consists of two distinct interface trees:

- The first tree starts with the `Collection` interface, which provides for the basic functionality used by all collections, such as `add` and `remove` methods. Its subinterfaces — `Set`, `List`, and `Queue` — provide for more specialized collections.

- The `Set` interface does not allow duplicate elements. This can be useful for storing collections such as a deck of cards or student records. The `Set` interface has a subinterface, `SortedSet`, that provides for ordering of elements in the set.

- The `List` interface provides for an ordered collection, for situations in which you need precise control over where each element is inserted. You can retrieve elements from a `List` by their exact position.

- The `Queue` interface enables additional insertion, extraction, and inspection operations. Elements in a `Queue` are typically ordered in on a FIFO basis.

- The `Deque` interface enables insertion, deletion, and inspection operations at both the ends. Elements in a `Deque` can be used in both LIFO and FIFO.

- The second tree starts with the `Map` interface, which maps keys and values similar to a `Hashtable`.

- `Map`'s subinterface, `SortedMap`, maintains its key-value pairs in ascending order or in an order specified by a `Comparator`.

These interfaces allow collections to be manipulated independently of the details of their representation.

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