arrays class presentation

Introduction to Computer ProgrammingLab 2

Arrays

Neveen Reda

Arrays in action0There are many uses for arrays0For example image pixels are represented using

arrays

Neuroph (2012)

Arrays in action

0Arrays can also be used in creating grids for games.

Eckert (2009)

Lesson Objectives

After this lesson you will be able to:

1.Develop Java programs that create arrays and perform different operations on them.

2.Determine the functionality and output of any given program that performs array manipulations.

Arrays0 Why arrays?

Individual variables can only hold one value at a time, Arrays can holds multiple values (Abdennadher , 2010).

0 “An array is a data structure that defines an indexed collection of a fixed number of data elements.” (Mughal & Rasmussen, 2009).

Arrays0 The position of an element in an array is called the index.0 If array X contains 10 elements, the first element will be at

position (index) '0' and the last element is at position '9'

Oracle (2012)

Arrays Declarations0 All the elements in an array have the same data type.

(For example all integers, all Strings, all doubles and so on)

Examples:

int [] x; //x is an array of integers.

double [] myArray; //myArray is an array of doubles.

Creating Arrays0 The size if an array is fixed. It is specified when the array is

created and cannot be changed (Abdennadher , 2010).

x = new int[5]; //array x is now of size 5

myArray = new double[3];

Creating Arrays0 An array can be declared and created in one statement.0 Until this point the arrays is empty (contains default values

of its declared type)

Examples:

int [] x = new int [5];

double [] myArray = new double [3];

int number = 10;

char [] letters = new char[number];

Initializing Arrays

Double [] prices = new double [5];

Initializing Arrays

Double [] prices = {2.25, 3.0, 10.5, 5.3, 0.5};

2.25

3.0

10.5

5.3

0.5

Using ArraysAfter creating and initializing an array, it can be used

within a program:

1. An element in the array can be used within a statement

2. The reference to the array can be used within a statement. (Abdennadher , 2010)

Using Arrays0 Reassign value to index:

0 Using element within a statement:

3.0

10.5

5.3

0.5

Prices[0] = 4.5;

if(Prices[1] >= 3.0){

Discount = 10;

}

2.254.5

Array Examples

0 Write a java program that creates an array of size 3 and prints all its elements using a for loop.

References• Abdennadher S. (2010). Arrays. Lecture notes.

• Eckert T. (2009). Bimaru - Battleship Solitaire [image]. Retrieved from: http://www.cyrket.com/p/android/com.androidcan.bimaru/

• Mughal K. A. & Rasmussen R. W. (2009). A Programmer's Guide to Java SCJP Certification. Upper Saddle River, NJ: Pearson Education.

• Neuroph (2012). Image colors [image]. Retrieved from: http://neuroph.sourceforge.net/image_recognition.html

• Oracle (2012). An array of 10 elements [image]. Retrieved from: http://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html