19.1 ArrayList

An ArrayList encapsulates an ordered list of objects, much like Java's Vector or ArrayList classes. Each ArrayList object has an initial capacity (accessible via the public property Capacity ) which automatically expands as more elements are inserted into the ArrayList object.

The example below shows some common methods which you can use with ArrayList .

 1: using System;  2: using System.Collections;  3:  4: public class TestClass{  5:   public static void Main(){  6:  7:     String item1 = "apple",  8:            item2 = "orange",  9:            item3 = "banana", 10:            item4 = "durian", 11:            item5 = "strawberry"; 12: 13:     ArrayList al = new ArrayList(); 14: 15:     // Use of  Add  . New elements are inserted behind. 16:     al.Add(item1); 17:     al.Add(item2); 18:     al.Add(item3); 19:     al.Add(item4); 20:     al.Add(item5); 21: 22:     // Use of  Contains  and  IndexOf  23:     Console.WriteLine 24:       ("al contains orange : " + al.Contains("orange")); 25:     Console.WriteLine 26:       ("Index of orange : " + al.IndexOf("orange")); 27:     PrintCollection(al); 28:     Console.WriteLine("------------------------------"); 29: 30:     // Use of  Insert  . Unlike Add, you can specify a 31:     // position to insert an element. 32:     Console.WriteLine("Inserting peach at index 1..."); 33:     al.Insert(1,"peach"); 34:     Console.WriteLine 35:       ("Index of peach  : " + al.IndexOf("peach")); 36:     Console.WriteLine 37:       ("Index of orange : " + al.IndexOf("orange")); 38:     PrintCollection(al); 39:     Console.WriteLine("------------------------------"); 40: 41:     // Use of  Count  public property 42:     Console.WriteLine("Count: " +al.Count); 43: 44:     // Use of  Remove  45:     PrintCollection(al); 46:     Console.WriteLine("Removing banana..."); 47:     al.Remove("banana"); 48:     PrintCollection(al); 49:     Console.WriteLine("------------------------------"); 50: 51:     // Use of  Sort  52:     PrintCollection(al); 53:     Console.WriteLine("Sorting..."); 54:     al.Sort(); 55:     PrintCollection(al); 56:     Console.WriteLine("------------------------------"); 57: 58:     // Use of  ToArray  . ToArray returns an object array 59:     Console.WriteLine("Creating new array..."); 60:     object[] myArray = al.ToArray(); 61:     Console.WriteLine("Array size: " + myArray.Length); 62:   } 63: 64:   // prints out all elements of the ArrayList object 65:   public static void PrintCollection(ArrayList al){ 66:       Console.Write("Elements: "); 67: 68:       IEnumerator enumerator = al.  GetEnumerator  (); 69: 70:       while (enumerator.MoveNext()) 71:          Console.Write(enumerator.Current + ","); 72: 73:       Console.WriteLine(""); // new line 74:   } 75: } 

Output:

 c:\expt>test al contains orange : True Index of orange : 1 Elements: apple,orange,banana,durian,strawberry, ------------------------------ Inserting peach at index 1... Index of peach  : 1 Index of orange : 2 Elements: apple,peach,orange,banana,durian,strawberry, ------------------------------ Count: 6 Elements: apple,peach,orange,banana,durian,strawberry, Removing banana... Elements: apple,peach,orange,durian,strawberry, ------------------------------ Elements: apple,peach,orange,durian,strawberry, Sorting... Elements: apple,durian,orange,peach,strawberry, ------------------------------ Creating new array... Array size: 5