Introduction
ArrayList implements the IList interface using an array whose size is dynamically increased as required. In this article I explain how to create the ArrayList and the various methods and properties of the ArrayList.
Creation of ArrayList
To create the ArrayList the following code is used:
ArrayList arr = new ArrayList();
The datatype of an ArrayList is object type, so we can add the elements having the datatype string, integer and any other.
Add the elements in ArrayList
To add values, the Add() method is used.
The following code describes how we add the elements to the ArratList.
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList();
arr.Add("Sunday");
arr.Add("Monday");
arr.Add("Tuesday");
arr.Add("Wednesday");
arr.Add("Thusday");
arr.Add("Friday");
arr.Add("Saturday");
Console.WriteLine("The elements of the ArrayList are:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
}
}
}
Output
![arraylist_add.jpg]()
Properties
Capacity
Gets or sets the number of elements that the ArrayList can contain. The default capacity of an ArrayList is 4. If I add 5 elements then its capacity becomes doubled (that is 8) relative to the previous one (that is, 4).
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList();
arr.Add("Sunday");
arr.Add("Monday");
Console.WriteLine("**********Elements of ArrayList*************");
Console.WriteLine();
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
Console.WriteLine();
Console.WriteLine("Capacity of the ArrayList is:" + arr.Capacity);
Console.WriteLine();
Console.WriteLine("//Adding Three more elements");
Console.WriteLine("**********Elements of ArrayList*************");
Console.WriteLine();
arr.Add("Tuesday");
arr.Add("Wednesday");
arr.Add("Thusday");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
Console.WriteLine();
Console.WriteLine("Now the Capacity is:" + arr.Capacity);
Console.WriteLine();
Console.WriteLine("//Adding Four more elements");
Console.WriteLine("**********Elements of ArrayList*************");
arr.Add("Friday");
arr.Add("Saturday");
arr.Add("Januray");
arr.Add("Feburay");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
Console.WriteLine();
Console.WriteLine("Now the Capacity is:" + arr.Capacity);
}
}
}
Output
![arraylist_capacity.jpg]()
Count
Gets the number of elements actually contained in the ArrayList.
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList();
arr.Add("Sunday");
arr.Add("Monday");
Console.WriteLine("**********Elements of ArrayList*************");
Console.WriteLine();
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
Console.WriteLine();
Console.WriteLine("The number of element in the ArrayList are:" + arr.Count);
Console.WriteLine();
Console.WriteLine("//Adding Three more elements");
Console.WriteLine("**********Elements of ArrayList*************");
Console.WriteLine();
arr.Add("Tuesday");
arr.Add("Wednesday");
arr.Add("Thusday");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
Console.WriteLine();
Console.WriteLine("Now the number of elements in the ArrayList are:" + arr.Count);
Console.WriteLine();
Console.WriteLine("//Adding Four more elements");
Console.WriteLine("**********Elements of ArrayList*************");
arr.Add("Friday");
arr.Add("Saturday");
arr.Add("Januray");
arr.Add("Feburay");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
Console.WriteLine();
Console.WriteLine("Now the elements in the ArrayList are:" + arr.Count);
}
}
}
Output
![arraylist_count.jpg]()
Methods
Clear()
Removes all elements from the ArrayList.
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList(7);
arr.Add("Sunday");
arr.Add("Monday");
arr.Add("Tuesday");
arr.Add("Wednesday");
arr.Add("Thusday");
arr.Add("Friday");
arr.Add("Saturday");
Console.WriteLine("The elements in the arraylist are:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
Console.WriteLine("The number of element in the arraylist are:" + arr.Count);
arr.Clear();
Console.WriteLine("After apply the clear method the elements in the arraylist are:" + arr.Count);
}
}
}
Output
![arraylist_clear.jpg]()
Contains()
Determines whether an element is in the ArrayList.
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList(7);
arr.Add("Sunday");
arr.Add("Monday");
arr.Add("Tuesday");
arr.Add("Wednesday");
arr.Add("Thusday");
arr.Add("Friday");
arr.Add("Saturday");
Console.WriteLine("The elements in the arraylist are:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
Console.WriteLine();
Console.WriteLine("The element Saturday contain in the arraylist is:" + arr.Contains("Saturday"));
Console.WriteLine("The element Monday contain in the arraylist is:" + arr.Contains("Monday"));
Console.WriteLine("The element Tuesday contain in the arraylist is:" + arr.Contains("Tuesday"));
Console.WriteLine("The element May contain in the arraylist is:" + arr.Contains("May"));
Console.WriteLine("The element Hello contain in the arraylist is:" + arr.Contains("Hello"));
}
}
}
Output
![arraylist_contains.jpg]()
Insert()
Inserts an element into the ArrayList at the specified index.
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList(7);
arr.Add("Sunday");
arr.Add("Monday");
arr.Add("Tuesday");
arr.Add("Wednesday");
arr.Add("Thusday");
arr.Add("Friday");
arr.Add("Saturday");
Console.WriteLine("The elements in the arraylist are:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
arr.Insert(0, "********Names of the days*******");
arr.Insert(8, "*********Names of the months**********");
arr.Insert(9, "Janurary");
arr.Insert(10, "Feburary");
arr.Insert(11, "March");
arr.Insert(12, "April");
arr.Insert(13, "May");
Console.WriteLine("The elements in the arraylist are after the insert operation:");
Console.WriteLine();
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
}
}
}
Output
![arraylist_insert.jpg]()
InsertRange()
Inserts the elements of a collection into the ArrayList at the specified index.
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList(7);
arr.Add("Sunday");
arr.Add("Monday");
arr.Add("Tuesday");
arr.Add("Wednesday");
arr.Add("Thusday");
arr.Add("Friday");
arr.Add("Saturday");
Stack stack=new Stack();
stack.Push("Janurary");
stack.Push("Feburary");
stack.Push("March");
stack.Push("April");
stack.Push("May");
stack.Push("June");
stack.Push("July");
stack.Push("August");
stack.Push("September");
stack.Push("October");
stack.Push("November");
stack.Push("December");
Console.WriteLine("The elements in the arraylist are:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
arr.Insert(0, "********Names of the days*******");
arr.Insert(8, "*********Names of the months**********");
arr.InsertRange(9, stack);
Console.WriteLine("The elements in the arraylist are after the insert operation:");
Console.WriteLine();
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
}
}
}
Output
![arraylist_insertrange.jpg]()
IndexOf(object)
Searches for the specified object and returns the zero-based index of the first occurrence within the entire ArrayList.
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList(7);
arr.Add("Sunday");
arr.Add("Monday");
arr.Add("Tuesday");
arr.Add("Wednesday");
arr.Add("Thusday");
arr.Add("Friday");
arr.Add("Saturday");
Console.WriteLine("The elements in the arraylist are:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
Console.WriteLine("The index value of Sunday is:" + arr.IndexOf("Sunday"));
Console.WriteLine("The index value of Monday is:" + arr.IndexOf("Monday"));
Console.WriteLine("The index value of Tuesday is:" + arr.IndexOf("Tuesday"));
Console.WriteLine("The index value of Wednesday is:" + arr.IndexOf("Wednesday"));
Console.WriteLine("The index value of Thusday is:" + arr.IndexOf("Thusday"));
Console.WriteLine("The index value of Friday is:" + arr.IndexOf("Friday"));
Console.WriteLine("The index value of Saturday is:" + arr.IndexOf("Saturday"));
}
}
}
Output
![arraylist_indexof.jpg]()
Remove()
Removes the first occurrence of a specific object from the ArrayList.
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList(7);
arr.Add("Sunday");
arr.Add("Monday");
arr.Add("Tuesday");
arr.Add("Wednesday");
arr.Add("Thusday");
arr.Add("Friday");
arr.Add("Saturday");
Console.WriteLine("The elements in the arraylist are:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
arr.Remove("Sunday");
arr.Remove("Monday");
arr.Remove("Tuesday");
Console.WriteLine();
Console.WriteLine("After remove the elements the arraylist is as:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
}
}
}
Output
![arraylist_remove.jpg]()
RemoveAt()
Removes the element at the specified index of the ArrayList.
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList(7);
arr.Add("Sunday");
arr.Add("Monday");
arr.Add("Tuesday");
arr.Add("Wednesday");
arr.Add("Thusday");
arr.Add("Friday");
arr.Add("Saturday");
Console.WriteLine("The elements in the arraylist are:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
arr.RemoveAt(3);
arr.RemoveAt(1);
arr.RemoveAt(2);
Console.WriteLine();
Console.WriteLine("After remove the elements the arraylist is as:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
}
}
}
Output
![arraylist_removeat.jpg]()
RemoveRange()
Removes a range of elements from the ArrayList.
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList(7);
arr.Add("Sunday");
arr.Add("Monday");
arr.Add("Tuesday");
arr.Add("Wednesday");
arr.Add("Thusday");
arr.Add("Friday");
arr.Add("Saturday");
Stack stack = new Stack();
stack.Push("Janurary");
stack.Push("Feburary");
stack.Push("March");
stack.Push("April");
stack.Push("May");
stack.Push("June");
stack.Push("July");
stack.Push("August");
stack.Push("September");
stack.Push("October");
stack.Push("November");
stack.Push("December");
Console.WriteLine("The elements in the arraylist are:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
arr.Insert(0, "********Names of the days*******");
arr.Insert(8, "*********Names of the months**********");
arr.InsertRange(9, stack);
Console.WriteLine("The elements in the arraylist are after the insert operation:");
Console.WriteLine();
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
arr.RemoveRange(9, 12);
Console.WriteLine();
Console.WriteLine("After apply the RemoveRange operation the elements are:");
Console.WriteLine();
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
}
}
}
Output
![arraylist_removerange.jpg]()
Reverse()
Reverses the order of the elements in the entire ArrayList.
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList();
arr.Add(1);
arr.Add(23);
arr.Add(12);
arr.Add(11);
arr.Add(45);
arr.Add(20);
arr.Add(54);
Console.WriteLine("The elements in the arraylist are:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
arr.Reverse();
Console.WriteLine("After apply reverse methods the elements are as:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
}
}
}
Output
![arraylist_reverse.jpg]()
Sort()
Sorts the elements in the entire ArrayList.
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList();
arr.Add(1);
arr.Add(23);
arr.Add(12);
arr.Add(11);
arr.Add(45);
arr.Add(20);
arr.Add(54);
Console.WriteLine("The elements in the arraylist are:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
arr.Sort();
Console.WriteLine("After apply sort methods the elements are as:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
}
}
}
Output
![arraylist_sort.jpg]()
BinarySearch(object)
Searches the entire sorted ArrayList for an element using the default comparer and returns the zero-based index of the element.
For example:
namespace ArrayList1
{
class Program
{
static void Main(string[] args)
{
ArrayList arr = new ArrayList();
arr.Add(1);
arr.Add(23);
arr.Add(12);
arr.Add(11);
arr.Add(45);
arr.Add(20);
arr.Add(54);
Console.WriteLine("The elements in the arraylist are:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
arr.Sort();
Console.WriteLine("The sorted list is as:");
foreach (object obj in arr)
{
Console.WriteLine(obj);
}
Console.WriteLine("The element 23 searched at:"+arr.BinarySearch(23));
Console.WriteLine("The element 12 searched at:" + arr.BinarySearch(12));
}
}
}
Output
![arraylist_binarysearch.jpg]()
Summary
In this article I explained the ArrayList and the various methods and properties of ArrayList.