Java Collections Framework

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The Java Collections Framework provides a set of classes and interfaces for representing and manipulating groups of objects, or collections. It includes a wide range of data structures such as Lists, Sets, Maps, Queues, and many more.

Here is a brief overview of some of the most commonly used interfaces and classes in the Java Collections Framework:

  • Collection: This is the root interface for all collection classes. It provides the basic functionality for storing, retrieving, and manipulating groups of objects. The most commonly used subinterfaces of Collection are List, Set, and Queue.

  • List: This interface extends Collection and represents an ordered collection of elements. Elements can be added, removed, and accessed by index.

  • Set: This interface extends Collection and represents an unordered collection of unique elements. Elements can be added and removed, and duplicate elements are not allowed.

  • Map: This interface represents a mapping between keys and values. Each key can map to only one value. The most commonly used implementation of Map is HashMap.

  • Queue: This interface extends Collection and represents a collection of elements that can be accessed in a first-in, first-out (FIFO) order. The most commonly used implementation of Queue is LinkedList.

  • ArrayList: This class implements the List interface and provides a resizable array that can be used to store elements. It is similar to an array, but its size can be dynamically adjusted as elements are added or removed.

  • LinkedList: This class implements both the List and Queue interfaces and provides a linked list that can be used to store elements. It is particularly useful for adding or removing elements from the beginning or end of the list.

  • HashSet: This class implements the Set interface and provides a hash table that can be used to store elements. It provides constant-time performance for adding and removing elements, but does not guarantee any particular order of iteration.

  • TreeSet: This class implements the Set interface and provides a red-black tree that can be used to store elements. It maintains the elements in sorted order and provides log-time performance for adding, removing, and accessing elements.

  • HashMap: This class implements the Map interface and provides a hash table that can be used to store key-value pairs. It provides constant-time performance for adding and removing elements, but does not guarantee any particular order of iteration.

  • TreeMap: This class implements the Map interface and provides a red-black tree that can be used to store key-value pairs. It maintains the elements in sorted order and provides log-time performance for adding, removing, and accessing elements.

These are just a few examples of the many classes and interfaces provided by the Java Collections Framework. By using these classes and interfaces, you can easily manipulate groups of objects and perform common operations such as searching, sorting, and filtering.