Java Collections Framework in Depth with Example for Beginners

Introduction to Java Collection

Java is by far one of the most extensively used programming languages of the IT world. It has been specially designed for specific use in the distributed ecosystem of the internet. Java is the language used for software development purposes for multiple platforms. When a software developer writes any Java application, the compiled code which is created (known as bytecode) is able to run on most of the operating systems (OS)Windows, Linux and Mac OS are to name a few. Java acquires much of its structure from the C and C++ programming languages.

Java has many frameworks in it such as Hibernate, Collections, Vaadin etc. Frameworks are usually used as a term for large bodies (usually many classes) of several prewritten java codes to which you can add on your own code in order to solve a problem pertaining to a specific domain. You can easily make use of a Java framework by simply calling its methods, supplying "callbacks" and inheritance, listeners, or its several other implementations of the Observer pattern. Today, we shall discuss “Java Collections”. Java Collection framework is a very popular framework of Java which provides a strong architecture to store or easily control the group of objects. For the purpose of better understanding.

The Blog Is Divided Into The Following Parts:

• Introduction to Java Collection
• History of Java Collection
• Core Java Collections Framework
• The ingredients of a Java Collection Framework
• Description of various Java Collection Framework hierarchy elements
• Java Collection Maps 

Introduction to Java Collection Framework 

The very famous “Java Collections Framework” is nothing but a gathering of many interfaces as well as object classes which helps a developer of the programmer in effectively and efficiently storing and processing the class and platform data. This framework comprises of many advantageous classes that have in turn got a lot of helpful Java functions to do which ultimately makes a programmer’s or developer’s task very easy.

History of Java Collection

The collections framework in Java was enthusiastically designed by Java engineers to specially meet the goals that they had envisaged. Their vision was to have-

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• The Java framework that could prove to be high-performance and low-maintenance. The implementations necessary for the purpose of fundamental collections (dynamic arrays, linked lists, trees, and hash tables) were required to be highly efficient.
• The framework had to consent to work, store and process different types of collections to work in a parallel manner and with a high amount of interoperability.
• The framework had to expand and/or adapt to a given collection without difficulty.

Core Java Collections Framework 

The collection is a representation of a group of objects. Solely depending on the process which has been used for the storing and retrieving, core collections are basically divided into three parts –

• Set- a Set collection of your framework does not contain duplicate values,
• List- List collection can contain the duplicate values which are stored in it sequentially.
• Queue- Queue collection contains an ordered list of objects with its usage specifically limited to inserting of the elements at the end of the list

The ingredients of a Java Collection Framework? 

A collections framework in Java is an amalgamated architecture for demonstrating java collections. All of the collections frameworks of Java comprise of the following –

• Interfaces− Interfaces are abstract type data that usually represents the collections. Interfaces agree to the collections to be maneuvered autonomously of the particulars of their demonstration. In languages like Java or we can say object-oriented languages, interfaces usually form a hierarchy.
• Implementations or Classes− These are the tangible implementations of the Java collection interfaces. In real meaning, they are data structures which are reusable.
• Algorithms− Algorithms are the methods that carry out useful data processing, such as probing and categorization, on various objects that put into practice the Java collection interfaces. The algorithms are known to be polymorphic meaning thereby that the identical method can be easily used for many different implementations of the proper collection interface.

In addition to the collections, this framework defines a number of map interfaces and java classes. Maps are the collection that store key/value pairs. Although maps are not collections per se in the proper usage of this term, they are fully incorporated into collections. A map of a java collection cannot hold duplicate keys; which means that each key can map only to one value at most.

Java Collection Framework Hierarchy Elements

Here is a list of various elements given in the screenshot below along with their descriptions-

ArrayList

This element tools all of the optional list operations, and allows all the elements, including the null ones. In addition to executing the List interface, this class supplies various methods to maneuver the size of the given array that is used inside to store the list.

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Vector

This class is approximately corresponding to ArrayList apart from the fact that it is coordinated.

LinkedList

Linked list implements elements of both parts of a collection ie List as well as the Queue interfaces.  It seamlessly executes all controlled operations and allows all the elements together with the null elements.

Priority Queues

Priority queues are the queues that order elements in consonance to an abounding comparator or in the nature of the elements’ natural order. 

HashSet 

This class executes the Set part of the collection interface and is substantially backed by a hash table (actually a HashMap instance). Though it makes no guarantees with regard to the iteration order of the set part; in particular, it does not promise that the order will remain intact for good, over the time. This class also permits the null elements of the interface.

LinkedHashSet

Hash table and linked list execution of the Set framework, with conventional iteration order. This execution differs from HashSet in that it supports and takes care of a doubly-linked list managing all the way through all of its entries.

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TreeSet

Treeset allows an easy execution of the Set interface that utilizes a tree kind of structure for storage. Objects are stored in a well organized and ascending order. Admission and recovery times are fairly fast, which make TreeSet an outstanding choice when storing of large amounts of sorted data sets that must be found swiftly.

Java Collection Maps

Without the Map interface, the collection is not complete.The Java collection classes encompass of two main root interfaces of Java collection classes. One is The Collection interface (java.util.Collection) and the other is the Map interface (java.util.Map)

• AbstractMap: Executes almost all the parts of the Map interface.
• HashMap: The HashMap class utilizes a hashtable to substantially execute the Map interface.
• TreeMap: Stretch the AbstractMap to utilize a tree structure.
• WeakHashMap: Stretches the AbstractMap to utilize a hash table with scrawny keys.
• LinkedHashMap: Stretches a HashMap to permit insertion-order iterations.
• IdentityHashMap: Stretches an AbstractMap and utilizes orientation equal opportunity when comparing several documents. 

Java Collection framework Summary

The collection framework is the answer to the much needed central and unifying theme which is required to effectively handle the group of objects in Java framework. This is because as discussed already Collection Framework in java is a centralized as well as an amalgamated theme to store and stage-manage the group of objects in the Java frameworks. Java Collection Framework lets you have some really cool pre-defined classes along with the interfaces to efficiently handle the group of objects in it. Check Spring Framework.

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