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();
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:
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
Press any key to continue . . .
