ARRAYLIST CLASS

ARRAYLIST CLASS

An array list is very similar to an array, except that it has the ability to grow. It is represented by the class System.Collections.ArrayList.

The simplest form of instantiation of an ArrayList is illustrated here:

ArrayList baseballTeams = new ArrayList();

  In order to get at the ArrayList class, user need to make a reference to the System.Collections namespace in your project. User can  instantiate an ArrayList by indicating the initial capacity user want. For example:

ArrayList baseballTeams = new ArrayList(20);

It is also possible to set the capacity of the ArrayList directly after a generic instantiation with the use of the Capacity property as shown in the following example:

ArrayList baseballTeams = new ArrayList();

baseballTeams.Capacity = 20

Once the ArrayList is instantiated, user can then add elements using the Add() method. This console application example uses the Add() method and then displays each of the items that were added:

ArrayList baseballTeams = new ArrayList();

baseballTeams.Add("St. Louis Cardinals");

One thing to note about adding items to the ArrayList is that the ArrayList treats all its elements as object references. That means you can store whatever objects user like in an ArrayList, but when accessing the objects, user will need to cast them back to the appropriate data type, as shown here:

string element1 = (string)baseballTeams[1];

When adding items to the ArrayList, user can also specify the location of the item being added using the Insert() method. This is illustrated in the following example:

baseballTeams.Insert(1, "San Francisco Giants"); // inserts at position 1

User can remove elements at a specific point in the collection with the use of the RemoveAt() method. This is done using the following construction:

baseballTeams.RemoveAt(1); // removes object at position 1

SOME IMPORTANT ARRAYLIST METHODS AND PROPERTIES

Methods/property	Description
Add() Clear() Contains() CopyTo() Insert() Remove() RemoveAt() RemoveRange() Sort() Capacity Count	Adds an object to a list Removes all the elements from the list Determines if an element is in the list Copies a list to another Inserts an element into the list Removes the first occurrence of an element Removes the element at the specified place Remove a range of elements Sorts the element Gets or sets the number of elements in the list Gets the number of elements currently in the list

using System;

using System.Text;

using System.Collections;

   class Program

    {

        static void Main(string[] args)

        {   //Creating an ArrayList

            ArrayList names = new ArrayList();

            //Adding the elements to the ArrayList

            Console.WriteLine("Using Add().......");

            names.Add("Aditya Tyagi");//Add(Object obj)

            names.Add("Dev Pratap");

            names.Add("Arun Kumar");

            names.Add("Arun Solanki");

            names.Add("Deepak");

            names.Add("Rajesh");

            for (int i = 0; i < names.Count; i++)

            {

                Console.WriteLine(names[i]);

            }

            //Using Remove()

            Console.WriteLine("Using Remove()........");

            names.Remove("Rajesh");Remove(object obj)

            for (int i = 0; i < names.Count; i++)

            {

                Console.WriteLine(names[i]);

            }

            //Using RemoveAt()

            Console.WriteLine("Using RemoveAt().......");

            names.RemoveAt(4);//RemoveAt(int index)

            for (int i = 0; i < names.Count; i++)

            {

                Console.WriteLine(names[i]);

            }

            //Using Insert()

            Console.WriteLine("Using Insert().......");

            names.Insert(4, "Deepak");//Insert(int index,object obj)

            names.Insert(5, "Rajesh");

            for (int i = 0; i < names.Count; i++)

            {

                Console.WriteLine(names[i]);

            }

            //Using RemoveRange()

            Console.WriteLine("Using RemoveRange().......");

            names.RemoveRange(4, 2);//RemoveRange(int index,int count)

            for (int i = 0; i < names.Count; i++)

            {

                Console.WriteLine(names[i]);

            }

            //Using Sort()

            Console.WriteLine("Using Sort().......");

            names.Sort();

            for (int i = 0; i < names.Count; i++)

            {

                Console.WriteLine(names[i]);

            }

            //Using Contains()

            Console.WriteLine("Using Contains().......");

            bool b= names.Contains("Aditya Tyagi");//Contains(object obj)

            Console.WriteLine(b);

            //Using Clear()

            Console.WriteLine("Using Clear().......");

            names.Clear();

            Console.WriteLine(names.Count);

           

            

        }

    }

Output:

Using Add().......

Aditya Tyagi

Dev Pratap

Arun Kumar

Arun Solanki

Deepak

Rajesh

Using Remove()........

Aditya Tyagi

Dev Pratap

Arun Kumar

Arun Solanki

Deepak

Using RemoveAt().......

Aditya Tyagi

Dev Pratap

Arun Kumar

Arun Solanki

Using Insert().......

Aditya Tyagi

Dev Pratap

Arun Kumar

Arun Solanki

Deepak

Rajesh

Using RemoveRange().......

Aditya Tyagi

Dev Pratap

Arun Kumar

Arun Solanki

Using Sort().......

Aditya Tyagi

Arun Kumar

Arun Solanki

Dev Pratap

Using Contains().......

True

Using Clear().......

0

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