C Sharp for Java programmer -Beginners Guide Chapter 1.1


Arrays

Creating Arrays

An array is a type of object that contains values called elements. Every elements of an array must contain same type of values.

Array is like Objects and they are created with new Keyword. Array indexes start at ZERO.

Declarations

  • Single - Dimensional Arrays.  

    int[ ] num;                      // Declaration , Here, it does not allocate any Storage.

    num = new int[3];           // Construction with Size. As Array type is int, Elements will be 

                                       //  initialized with 0.
    Or

    int[ ] num= new int[3];          // Declaration and Construction both done together.


    So, what we have done till now

    1. We have declared an Array called num, which is having five elements and type of the Array is Integer, so elements value will be initialized with 0  and Index value will be 0 to 4 that is, num[0] to num[3].

    int[] num= new int[] { 7, 8, 6}; // Declaration ,Construction & Initialization.


  • Multi - Dimensional Arrays

    int[ , ] num;                   // Declaration , Here, it does not allocate any Storage.

    num = new int[3,2];        // Construction with Size. As Array type is int, Elements will be 

                                      //  initialized with 0.


    Or

    int[ ] num= new int[3,2];        // Declaration and Construction both done together.


    Or

    int[ , ] num= new int[ ] { 7, 8},{6,7),{8,6); // Declaration ,Construction & Initialization.


  • Jagged Arrays - Array of Arrays

    int [][] num;

    num = new int[3][];         //Single Dimensional Array with three elements.

    num[0] = new int[3];       // 1st Element with 3 integers.

    num[1] = new int[4];       //  2nd Element with  4 integers

    num[2] = new int[5];       // 3rd Element with 5 integers.


    Or

    With values.

    num[0] = new int[] {0,1,2);

    num[1] =new int[] {1,2,3); 

Example 1: To Practice this,

Go to Start --> Programs --> Ms Visual Studio 2003 --> New Project --> Visual C# Project --> Console Application.

using System;

class Ms_Array1

{

          static void Main(string[] args)

          {

               int[] num;

               num = new int[3];

               Console.WriteLine (num[0]);

               Console.WriteLine (num[1]);

               Console.WriteLine (num[2);

           }

}

Example 2:

using System;

class Ms_Array2

{

     static void Main(string[] args)

     {

        int[] num;

        num = new int[3];

        Console.WriteLine (num[0]);

        Console.WriteLine (num[1]);

        Console.WriteLine (num[2);

        Console.WriteLine (num[3); // Error , Because Indexed Value is 0 to 2.

     }

 }

Question 1 - What will happen when you compile it and Run it?

using System;

class Msq1_Array

{

    static void Main(string[] args)

    {

       int[] num= new int[3];

       Console.WriteLine (num[3]);

    }

}

  1. Compilation Error.
  2. Compilation and Output will be 0.
  3. System.IndexOutOfRangeException.
  4. Compilation and Output will be 3.

Question 2 - What will happen when you compile it and run it?

using System;

class Msq1_Array

{

   static void Main(string[] args)

   {

      int num[]= new int[3];

      Console.WriteLine (num[2]);

   }

}

  1. Compilation and Output will be 0.
  2. Compilation Error.
  3. Compilation and Output will be 2.
  4. Compilation without any output.

Question 3 - What will happen when you compile it and run it?

using System;

class Msq3_Array

{

    static void Main(string[] args)

    {

       int num[]= new int[3];

       Console.WriteLine (num[0]);

    }

}

  1. Compilation and output will be Zero.
  2. Compilation errors.
  3. Compilation without output.
  4. Compilation but Run Time errors.