The document discusses arrays in Java. It defines arrays as variables that can store multiple values of the same type in contiguous memory locations. It describes how to declare, instantiate, initialize, access, and manipulate array elements. The key points covered are declaring arrays with the type[], accessing elements with indexes, initializing arrays during declaration, and setting and getting values at specific indexes.

2. At the end of the lesson, the student should be
able to:
 Declare and create arrays
 Access array elements
 Determine the number of elements in an
array
 Declare and create multidimensional arrays
 Describe how to use arrays to manage multiple
values in the same variable.

3. 

Suppose we have here three variables of type int
with different identifiers for each variable.
int number1;
int number2;
int number3;
number1 = 1;
number2 = 2;
number3 = 3;
As you can see, it seems like a tedious task in
order to just initialize and use the variables
especially if they are used for the same purpose.

4. In Java and other programming
languages, there is one capability wherein we
can use one variable to store a list of data
and manipulate them more efficiently. This
type of variable is called an array.
●
An array stores multiple data items of the
same data type, in a contiguous block of
memory, divided into a number of slots.
●

5. 
The Java programming language allows you
to group multiple values of the same type
(lists) using one-dimensional arrays. Arrays
are useful when you have related pieces of
data (such as the ages for several people),but
you do not want to create separate variables
to hold each piece of data

6. Array of int
0
Number:
1
2
0
1
2
Array of flowers

7. 
To declare an array, write the data type, followed by
a set of square brackets[], followed by the identifier
name.
Syntax: type [] array_identifier;
Where:
 The type represents the primitive data type or
object type for the values stored in the array.
 The [] informs the compiler that you are declaring
an array
 The array_identifier is the name that you are
assigning to refer to the array.
For example,
int []ages; or
int ages[];

8. After declaring, we must create the array and
specify its length with a constructor
statement.
Syntax: array_identifier = new type [length];
where:
 The array_identifier is the name you are
assigning to reference the array.
 The type represents the primitive data type or
object type for the value stored in the array.
 The length represent the size of the array.


9. 
Use the following code to instantiate an array
of char called status and an array of int called
ages.
status = new char [20];
ages = new int [5];

10. 
You can fill the contents of an array after you
have created the array. The syntax for setting
the values in an array is:
array_identifier[index] = value;
where:
 The array_identifier is the name you are


assigning to the array.
The index represents the location in the array
where the value will be placed.
The value is the value you are assigning to
index in the array.

11. ages[0]
ages[1]
ages[2]
ages[3]
ages[4]
ages:
0
19
=
=
=
=
=
19;
42;
92;
33;
46;
1
42
2
92
3
33
4
46

12. If you know the values you want in your array at the
time that you declare the array, you can declare,
instantiate, and set the values for an
Array object in the same line of code. The syntax for
this combined declaration, instantiation, initialization
of values is:

type [] array_identifier = {comma-separated_list_of_values_or_expressions};
where:
● The type represents the primitive data type or object type for the
values stored in the array.
● The [] informs the compiler that you are declaring an array.
● The array_identifier is the name you are assigning to the array.
● The {comma-separated_list_of_values_or_expressions}
represents a list of values you want to store in the array or a list of
expressions with results that will be stored in the array.

13. type [] array_identifier = {commaseparated_list_of_values_or_expressions};
where:
 The type represents the primitive data type or object
type for the values stored in the array.
 The [] informs the compiler that you are declaring an
array.
 The array_identifier is the name you are assigning to the
array.


The {commaseparated_list_of_values_or_expressions}
represents a list of values you want to store in the array
or a list of expressions with results that will be stored in
the array.

14. The following statement combines the
previous declaration, instantiation,
and initialization examples for the ages array

int [] ages = {19, 42, 92, 33, 46};

15. //creates an array of boolean variables with identifier
//results. This array contains 4 elements that are
//initialized to values {true, false, true, false}
boolean results[] = { true, false, true, false };
//creates an array of 4 double variables initialized
//to the values {100, 90, 80, 75};
double []grades = {100, 90, 80, 75};
//creates an array of Strings with identifier days and
//initialized. This array contains 7 elements
String days[]= {“Mon”,“Tue”,“Wed”,“Thu”,“Fri”,“Sat”,“Sun”};

16. Each element of an array is accessed using its
index. To access a value from the array, state the
array name and the index number for the element
(in braces []) on the right side of an assignment
operator.
The following code example demonstrates how to
set the value at a particular index in an array:
status[1] = 3
names[2] = “Johann";
ages[2] = 10;
prices[3] = 9.99F;

17. The following code example demonstrates
how to retrieve values from a particular index
in an array:
char s = status[1];
String name = names [2];
int age = ages[2];
double price = prices[3];
