What is the java collections hierarchy with example

Enid 173 Published: 09/24/2024

What is the java collections hierarchy with example

Here's the Java collections hierarchy with examples:

Collection Framework

Java's Collection Framework (JCF) provides a set of interfaces and classes that allow you to store, manipulate, and retrieve data efficiently. The framework consists of the following main components:

Collection: This is the top-level interface in the JCF, which represents a group of objects stored by means of a finite, unordered choice of a set of elements.

Example: List<String> list = new ArrayList<>();

Map: A Map is an unsorted collection of key-value pairs, where each key is unique and maps to a specific value.

Example: Map<String, Integer> map = new HashMap<>();

Hierarchy

Here's the hierarchy of classes and interfaces in the Java Collection Framework:

Collection

Set: A set is an unordered collection that allows no duplicate elements. Example: HashSet<String> set = new HashSet<>(); List: A list is an ordered collection that allows duplicates. Example: ArrayList<String> list = new ArrayList<>(); Queue: A queue is a first-in, first-out (FIFO) collection. Example: LinkedList<String> queue = new LinkedList<>(); Map HashMap: A hash map uses a hash function to map keys to values. Example: HashMap<String, Integer> map = new HashMap<>(); TreeMap: A tree map is a sorted map that orders entries based on their keys. Example: TreeMap<String, Integer> map = new TreeMap<>();

Interface Hierarchy

Here's the hierarchy of interfaces in the Java Collection Framework:

Collection Set NavigableSet: A navigable set is a set that allows navigation based on ordering.

Example: NavigableSet<String> set = new TreeSet<>();

SortedSet: A sorted set is a set that orders elements in some manner.

Example: SortedSet<String> set = new TreeSet<>();

List **LinkedList`: A linked list is an ordered collection where each element points to the next one.

Key Methods

Here are some key methods available on Java Collection Framework classes and interfaces:

add(E e): Adds an element to the end of a collection. contains(E e): Checks if a specific element exists in the collection. remove(E e): Removes the first occurrence of a specified element from the collection. size(): Returns the number of elements in the collection.

This is just a brief overview of the Java Collection Framework hierarchy and some key methods. I hope this helps! Let me know if you have any further questions.

What is the java collections hierarchy javatpoint

I'm glad you asked!

The Java Collections Hierarchy is a fundamental concept in Java programming that provides a framework for working with different types of data structures. In this context, "collections" refer to groups of objects that can be manipulated and processed as a whole.

According to the Java Documentation, the Collection Hierarchy is based on three main interfaces: Set, List, and Map. These interfaces are implemented by various classes in the java.util package, which provide different types of data structures for storing and manipulating collections.

1. Set Interface

The Set interface represents a collection that contains no duplicate elements. It provides methods such as add(), remove(), contains(), and size() to manipulate the set. Some examples of classes that implement the Set interface include HashSet, LinkedHashSet, and TreeSet.

2. List Interface

The List interface represents an ordered collection (i.e., a sequence) of elements, with indices that can be used to access specific elements. It provides methods such as add(), remove(), contains(), get(), and size() to manipulate the list. Some examples of classes that implement the List interface include ArrayList, LinkedList, Vector, and Stack.

3. Map Interface

The Map interface represents a collection that maps keys to values. It provides methods such as put(), remove(), containsKey(), get(), and size() to manipulate the map. Some examples of classes that implement the Map interface include HashMap, LinkedHashMap, TreeMap, and HashTable.

Hierarchy:

Here's a visual representation of the hierarchy:

          +---------------+
|  Collection   |
+---------------+
|
|
v
+-----------------+       +-----------------+
|        Set      |       |        List    |
+-----------------+       +-----------------+
|                             |
|                             |
v                             v
+-------------------+   +-----------------------+
|     HashSet     |   |  ArrayList        |
|  LinkedHashSet  |   |  LinkedList      |
|   TreeSet      |   |  Vector         |
|  ...           |   |  Stack         |
+-------------------+   +-----------------------+
|
|
v
+---------------+
|       Map     |
+---------------+
|
|
v
+---------------+
|    HashMap    |
|  LinkedHashMap|
|  TreeMap      |
|  HashTable  |
+---------------+

In summary, the Java Collections Hierarchy provides a framework for working with different types of data structures, including sets, lists, and maps. Understanding this hierarchy is crucial for effective programming in Java.

Would you like me to expand on any specific aspect?