Here you will learn what collections are and
how they can make your job easier and programs better.
The Collections Framework, first introduced with the Java 2 platform, Standard
Edition, version 1.2. The Collections Framework provides a well-designed set of
interfaces and classes for storing and manipulating groups of data as a single
unit, a collection.
What is Collection ?
A collection sometimes called a container. It
is the collection of Objects known as its elements ,collect into a single
place and treated as a single unit. these object can be store, retrieve,
manipulate as a elements of collection. Some collections allow duplicate
elements and others do not. Some are ordered and others unordered.
The Two "standard" constructors should be
provided by all the general-purpose Collection implementation classes.
A void (no arguments) constructor, which creates an empty
collection, and a constructor with a single argument of type Collection,
which creates a new collection with the same elements as its argument.
The Java Collections Application Programming Interface (API)
provide Java developers with a set of classes and interfaces for working with
groups of objects. The different interfaces describe the different types of
groups. For the most part, once you understand the interfaces, you understand
All collections frameworks contain the following:
- Interfaces: These are abstract data
types that represent collections. Interfaces allow collections to be
manipulated independently of the details of their representation.
- Implementations: These are the
concrete implementations of the collection interfaces. In essence, they are
reusable data structures.
- Algorithms: These are the methods
that perform useful computations, such as searching and sorting, on objects
that implement collection interfaces.
Collections Framework are divided into two
Classes implements these interfaces that are found in java.util package.
In the Collections
Framework, the interfaces Map and Collection are distinct with no lineage in the
hierarchy. The typical application of map is to provide access to values stored
When designing software with the Collection Framework, it is useful to remember
the following hierarchical relationship of the four basic interfaces of the
The Collection interface is a group of objects,
with duplicates allowed.
Set extends Collection but forbids duplicates.
List extends Collection also, allows duplicates and introduces positional
Map extends neither Set nor Collection
Description of these interfaces is given below.
Methods Of collection
In this program we use Array List Class and .
Create a Java program by using Eclipse ID. Open
the Eclipse and Follow these steps
Create a Java project and give the name
Here the name is Collection Demo.
Create the Class and gave the name
Here name of the class CollectionDemo. In this
program we insert some object in to the array list by using add() method of
Collection interface. The syntax of add() method is define below.
public boolean add(Object o)
we also use remove() and size()method in this program.
alg=new ArrayList<String>();//Generic Form
state array list size="+al.size());
inserting 7 elements array list size="+al.size());
array list items ="+al);
deleting 1 element from the array list then size ="+al.size());
array list items ="+al);
Compile and run the Program ,the output of
program is given below.