An array is an ordered collection that stores elements of the same type within a single variable name. Elements are accessed via an index number that starts at 0. Arrays can be declared with a type and size, then instantiated using new. Values are assigned using the index operator. The length property returns the number of elements in the array. Arrays are objects that are passed by reference, but intrinsic element types within arrays are passed by value.

1. Introduction to Arrays
Chapter 10

2. 10
What is an array?
An array is an ordered collection that
stores many elements of the same
type within one variable name.
Elements are the items in an array.
Each element is identified with an index
number.
Index numbers always start at 0 for the
first element.

3. 10
Declaring Arrays
Identify type of array
Use square brackets
int[] myArray;
Declares an array of int values

4. 10
Instantiating Arrays
Use the new keyword
Identify number of elements
myArray = new int[1000];
Instantiates myArray with 1000 elements
You can declare and instantiate in one
line
int[] myArray = new int[1000];

5. 10
Putting Values in the Array
Use the index operator to assign a
value at a particular place in the array.
myArray[10] = 100;
Assigns the value 100 to the 10th element
in the array
Most programs use a for loop to
iterate the array.

6. 10
Initializing the Array
You can initialize the array with values
at the same time the array is created.
int[] myArray = {1, 2, 3, 4, 5};

7. 10
Determining the Length of the Array
Use the length property to find the
number of elements in the array.
System.out.println(myArray.length);
Displays the length of the array in the console
For ( int i = 0; i < myArray.length;
i++ );
Uses the length property to set up the for loop

8. 10
Passing by Value
Intrinsic types are passed to methods
by value.
A copy of the value is passed.
The original value is unchanged.

9. 10
Passing by Reference
Objects are passed to methods by
reference.
The reference points to the original object.
A change to the object affects the object in the
calling method.

10. 10
Passing Arrays to Methods
An array is an object type.
Passed by reference
Elements of arrays are not necessarily
passed by reference.
Depends on the underlying element type
Extracting int elements from an array
and passing them to a method passes
them by value

11. 10
Using Polymorphic Objects
in an Array
An array can hold objects that:
Derive from the same base class
Implement a common interface