C# 0 The Complete Reference

sample

 is 

sample[0]

, and the last element is 

sample[9]

. For example, the 

following program loads 

sample

 with the numbers 0 through 9:

// Demonstrate a one-dimensional array.

using System;

class ArrayDemo {

  static void Main() {

    int[] sample = new int[10];

    int i;

    for(i = 0; i < 10; i = i+1)

      sample[i] = i;

    for(i = 0; i < 10; i = i+1)

      Console.WriteLine("sample[" + i + "]: " + sample[i]);

  }

}

The output from the program is shown here:

sample[0]: 0

sample[1]: 1

sample[2]: 2

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PART I

Chapter 7: 

Arrays and Strings 

139

PART I PART I

sample[3]: 3

sample[4]: 4

sample[5]: 5

sample[6]: 6

sample[7]: 7

sample[8]: 8

sample[9]: 9

Conceptually

, the 

sample

 array looks like this:

Arrays ar

e common in pr

ogramming because they let you deal easily with lar

ge numbers 

of r

elated variables. For example, the following pr

ogram finds the average of the set of values

 

stor

ed in the 

nums

 array by cycling thr

ough the array using a 

for

 loop:

// Compute the average of a set of values.

using System;

class Average {

  static void Main() {

    int[] nums = new int[10];

    int avg = 0;

    nums[0] = 99;

    nums[1] = 10;

    nums[2] = 100;

    nums[3] = 18;

    nums[4] = 78;

    nums[5] = 23;

    nums[6] = 63;

    nums[7] = 9;

    nums[8] = 87;

    nums[9] = 49;

    for(int i=0; i < 10; i++)

      avg = avg + nums[i];

    avg = avg / 10;

    Console.WriteLine("Average: " + avg);

  }

}

The output fr

om the pr

ogram is shown her

e:

Average: 53

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140

 

P a r t   I :  

T h e   C #   L a n g u a g e

Initializing an Array

In the preceding program, the 

nums

 array was given values by hand, using ten separate 

assignment statements. While that is perfectly correct, there is an easier way to accomplish 

this. Arrays can be initialized when they are created. The general form for initializing a one-

dimensional array is shown here:

type

[ ] 

array-name

 = { 

val1

,

val2

,

val3

, ..., 

valN

 };

Here, the initial values are specified by 

val1

 through 

valN.

 They are assigned in sequence, 

left to right, in index order. C# automatically allocates an array large enough to hold the 

initializers that you specify. There is no need to use the 

new

 operator explicitly. For example, 

here is a better way to write the 

Average

 program:

// Compute the average of a set of values.

using System;

class Average {

  static void Main() {

    int[] nums = { 99, 10, 100, 18, 78, 23,

                   63, 9, 87, 49 };

    int avg = 0;

    for(int i=0; i < 10; i++)

      avg = avg + nums[i];

    avg = avg / 10;

    Console.WriteLine("Average: " + avg);

  }

}

As a point of interest, although not needed, you can use 

new

 when initializing an array. 

For example, this is a proper, but redundant, way to initialize 

nums

 in the foregoing 

program:

int[] nums = new int[] { 99, 10, 100, 18, 78, 23,

                         63, 9, 87, 49 };

Although redundant here, the 

new

 form of array initialization is useful when you are 

assigning a new array to an already-existent array reference variable. For example:

int[] nums;

nums = new int[] { 99, 10, 100, 18, 78, 23,

                   63, 9, 87, 49 };

In this case, 

nums

 is declared in the first statement and initialized by the second.

One last point: It is permissible to specify the array size explicitly when initializing an 

array, but the size must agree with the number of initializers. For example, here is another 

way to initialize 

nums

:

int[] nums = new int[10] { 99, 10, 100, 18, 78, 23,

                           63, 9, 87, 49 };

In this declaration, the size of 

nums

 is explicitly stated as 10.

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