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Java Collections is a framework that provides a set of interfaces and classes to manage and manipulate groups of objects. Collections are used to store, retrieve, manipulate, and transmit data efficiently. In this blog, we will explore the Java Collections framework in depth and explain the different types of collections and their uses.
Java Collections Framework Hierarchy:
The Java Collections Framework consists of the following main interfaces:
Collection: The Collection interface is the root interface of the Java Collections Framework. It defines the basic operations that are common to all collection types, such as adding, removing, and querying elements.
List: The List interface extends the Collection interface and defines an ordered collection of elements. Elements can be accessed by their index position in the list.
Set: The Set interface extends the Collection interface and defines an unordered collection of unique elements. Duplicate elements are not allowed in a set.
Queue: The Queue interface extends the Collection interface and defines a collection that maintains the order in which elements are added. The Queue interface provides methods for adding, removing, and querying elements.
Map: The Map interface is used to store key-value pairs. Each key in a map is associated with a unique value. The Map interface provides methods for adding, removing, and querying key-value pairs.
Java Collections Framework Implementations:
The Java Collections Framework provides several implementations of the above interfaces:
ArrayList: ArrayList is a class that implements the List interface. It provides an ordered collection of elements that can be accessed by their index position in the list. ArrayList is implemented as a resizable array and is similar to the arrays in C or C++.
LinkedList: LinkedList is another class that implements the List interface. It provides a linked list data structure that allows efficient insertion and removal of elements at any position in the list.
HashSet: HashSet is a class that implements the Set interface. It provides an unordered collection of unique elements. Duplicate elements are not allowed in a HashSet.
TreeSet: TreeSet is another class that implements the Set interface. It provides an ordered collection of unique elements. The elements in a TreeSet are stored in a sorted order.
PriorityQueue: PriorityQueue is a class that implements the Queue interface. It provides a priority queue data structure that maintains the order in which elements are added.
HashMap: HashMap is a class that implements the Map interface. It provides a hash table data structure that stores key-value pairs. HashMap provides fast retrieval of key-value pairs.
TreeMap: TreeMap is another class that implements the Map interface. It provides a sorted map data structure that stores key-value pairs in a sorted order.
In conclusion, Java Collections is a powerful framework that provides a set of interfaces and classes to manage and manipulate groups of objects. The Java Collections Framework is used extensively in Java applications to store, retrieve, manipulate, and transmit data efficiently. By understanding the different types of collections and their uses, you can use the Java Collections Framework to write more efficient and effective Java code.
Here is a visual representation of the Java Collections Framework hierarchy and some of its implementations:
simple example (updating soon)
Iterable (interface)
|
Collection (interface)
/ | \
List (interface) Set (interface) Queue (interface)
/ \ / \ / \
ArrayList LinkedList HashSet Deque (interface) PriorityQueue
|_ ArrayDeque
Map (interface)
|
TreeMap
|
HashMap
This diagram shows that Collection is the root interface of the Java Collections Framework, and it has three sub-interfaces: List, Set, and Queue. Each of these interfaces has several implementations, such as ArrayList and LinkedList for List, HashSet and TreeSet for Set, and PriorityQueue for Queue.
The diagram also shows that Map is another interface of the Java Collections Framework, which has two implementations: TreeMap and HashMap. TreeMap provides a sorted map data structure that stores key-value pairs in a sorted order, while HashMap provides a hash table data structure that stores key-value pairs and provides fast retrieval.
Overall, this visual representation helps to show the relationships between the different interfaces and implementations of the Java Collections Framework.