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Collections Class in Java

Chitra Nachre
21st Feb 2019
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java collections

java collections

Collections in Java

Collection in simple terms means when a group of similar things, often a group created by someone is known as a collection. A collection when collected works like a container – it groups multiple similar elements into a single unit. Forming a natural group they can be stored, modify, redeem, recover and communicate aggregate data.

Java provides a collection framework defining several groups and interfaces to represent groups of objects as a single unit. Collection framework is one of the central and fundamental parts of Java programming language.

What Is Collection In Java

Collection in Java represents a single unit of the group. Using Java collection you can perform all the operations on the data like searching, sorting, inserting, manipulation, deletion, etc.

What is a framework in Java

A framework or software framework is the platform used for developing software applications. They are the large collected bodies of prewritten codes to which you add your own code in specific domains. It helps you dictate the structure of your application, by calling its methods, and inheritance.

Framework specializes classes to invoke the single method or procedures. It employs an inverted flow of control between itself and its clients. Using framework one can implement the call back functions, specialized classes, and interfaces.

What Is Collection Framework?

Java collection framework provides you with the complete architecture of objects. 

  • Java frameworks group of objects includes – classes, interfaces, and algorithm.
  • Class – Everything in Java is associated with classes and objects. Being a user-defined blueprint, a class in simple terms represents the data structure which is used again and again. It helps in creating objects. A class represents the common attributes and properties to the objects of one type.
  • Interface – Interface is the blueprint of class, specifying what a class should do. The interface in Java refers to an abstract “class” that is used to group related methods with “empty” bodies.
  • Algorithm – Algorithm refers to the process and the set of rules used to perform the operations such as searching and sorting.

Methods Of Collection Interface

Before learning about the methods of collection interface, you should first know what Collection Interface means. Collection Interface defines the most common methods that are applicable to any collection of the object.

There come various methods of Collection Interface, which are:

Methods of Collection Interface

Methods of Collection Interface

Iterator Interface in Java

Iterators are one of the predefined interfaces that are present in the java.util.*package. Iterator Interface’ main purpose is to provide the facility of iterating or extracting the elements of the collection in the only forward direction.

It Java collection it takes the place of Enumerations. By default, an object of the iterator is pointed out just before the first collection of any framework collection variable.

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Methods of Iterator Interface

Public boolean hasNext()

This method returns the true value if iteration has more elements in it, otherwise, false.

Public object next()

It helps you retrieve the next element of any collection framework.

remove()

This method helps you remove the last element returned by the iterator.

List Interface

It is a child interface of Collection, possessing an index-based method to insert and delete elements in it. It is helpful in declaring the behavior of a collection which stores a sequence of elements.

In its ordered collection of objects, it can store the duplicate values. List Interface is implemented by Array List, Linked List, Vector and Stack classes.

Java ArrayList

Array List being a part of collection framework helps you provide dynamic arrays in Java. It is slower than the other standard arrays but is very helpful in programs, where lots of manipulation in the array is required.

As the Java ArrayList class is non-synchronized, it is helpful in maintaining the insertion order.

Java LinkedList

LinkedList is way too different than the ArrayLists. Their structure of elements is not stored in contiguous locations. Each element of LinkedList is a separate object with a data part and address part. Due to this quality, they are preferred more than the Arrays.

Java LinkedList class is used as a list, stack or queue. However, Java LinkedList manipulation is fast because it requires no shifting needs.

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