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Chapter 6
Single-Dimensional
Arrays

Introduction
-An array is a data structure that can be used to store a collection of data
(elements) of the same type.
- Suppose, for instance, that you need to read 100 numbers, compute their
average, and find out how many numbers are above the average
-Instead of declaring individual variables, such as number_0, number_1, . . . ,
and number_99, you declare one array variable such as numbers and use
numbers[0], numbers[1], . . . , and numbers[99] to represent individual
variables.
- it more useful to think of an array as a collection of variables of the same
type.
Liang, Introduction to Java Programming, Eighth Edition, (c) 2011 Pearson Education, Inc. All rights reserved. 0132130807 MODIFIED BY: Abla Hussein

Introduction
-The array named number will look like following:
number[99]
number[98]
number[97]
.....
number[i]
.....
number[2]
number[1]
number[0]
90
72
88
…..
60
…..
55
45
70

Array Declaration
- The syntax for declaring an array variable is:
Example:
- The array can be any data type, and all elements in the array will have
the same data type.
datatype [ ] arrayName;
// or datatype arrayName [ ];
double [ ] marks; // double marks [ ];
int [ ] number; // int number [ ];

Array Creation
- The syntax for creating the array is:
-The array_size specifies the number of elements that can be stored in this
array.
Example:
- The size of an array cannot be changed after the array is created
arrayName = new datatype [array_size];
marks = new double [45];
number= new int [100];

Array Declaration and Creation
-Declaring and creating an array can be combined in one statement.
-The syntax for declaring and creating an array in one statement is:
Example:
datatype [ ] arrayName = new datatype [array_size];
or
datatype arrayName [ ] = new datatype [array_size];
double [ ] marks = new double [45];
int number [ ] = new int [100];

-We have declared and created the array, but we haven’t filled it yet!.
- The syntax for assigning (storing) a value at specific index in an array is:
- The index represents the position where the value will be stored in.
- The value must be in the data type of the array.
Example:
marks[4] = 72.0;
marks[30] = 87.0;
arrayName[index] = value;

Example:
---------------------------------------------------------------------------------
-
num
4
3
2
1
0
23
41
-13
18
4
vowels
4
3
2
1
0
‘u’
‘o’
‘i’
‘e’
‘a’
char [] vowels = new char[5];
vowels[0]= ‘a’;
vowels[1]= ‘e’;
vowels[2]= ‘i’;
vowels[3]= ‘o’;
vowels[4]= ‘u;
int [] num=new int [5];
num[0] = 4;
num[1] = 18;
num[2] = -13;
num[3] = 41;
num[4] = 23;

Array Default Values
- When an array is created, its elements are assigned the default values as
following:
default value
data type
zero 0
numeric data types
space
char data type
false
boolean data type
null
String data type

Array Initializers
- Java has a shorthand notation, known as the array initializer, which
combines the declaration, creation, and initialization of an array in one
statement.
-The syntax is:
Example:
- Array initializing has to be written in one statement. The following causes
syntax error:
datatype [ ] arrayName = {value_1 , value_2 , … , value_n};
int [ ] num;
num={4 , 18 , -13 , 41 , 23};
int [ ] num= {4 , 18 , -13 , 41 , 23};
char [ ] vowels= { ‘a’ , ‘e’ , ‘i’ , ‘o’ , ‘u’};

Array Size
-The syntax for finding the size of an array is:
Example:
arrayName.length;
int [ ] num= {4 , 18 , -13 , 41 , 23};
int size=num.length; // size=5

Array Index
-The array elements are accessed through the index. Array indices are zero
based; that is, they range from zero to arrayName.length-1.
-Each element in the array is represented using the following syntax:
Example:
-After an array is created, an indexed variable can be used in the same way
as a regular variable.
-Example:
arrayName[index];
int [ ] num= {4 , 18 , -13 , 41 , 23};
System.out.println(num[3]); // 41
num[2] = num[0]+num[1]; // num[2] = 22

Processing Arrays
-When processing array elements, you will often use a for loop.
Example :
int [ ] num= {4 , 18 , -13 , 41 , 23};
for(int i=0 ; i < num.length ; i++){
System.out.println(num[i]);
}

Processing Arrays
Q: write a program that defines an integer array of size 10, and prompts the user to
enter 10 numbers, stores it in an array and prints the numbers, and average of the
numbers.
Q: write a program to store the following temperatures in an array
25 , 14 , 34 , 8 , 14 , 7 , 32 , 18 , 15 , 22 , 40 , 38 , 14 , 21 , 28 , 40 , 19. then find
the following:
1. Print all the temperatures.
2. Find the sum and average of the temperatures.
3. Find the smallest temperature.
4. Find the largest temperature.
5. Find the index of temperature 32.
6. Find the smallest index of largest element.
7. How many times temperature 14 was repeated.

Processing Arrays
Q: write a program that prompts the user to enter his name, and puts the
name characters in an array.

Copying Arrays
-To copy the contents of one array, you have to create another array of the
same size and data type, then by using for loop you can copy the elements
of the first array to its corresponding indices in the second array.
Q: write a program to copy the following array into another one:
10.8
93
75.3
22
19
60
88
14.5
5
12.4

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