LEAPS Computing 2015 Ioannis Efstathiou ie24hwacuk slides originally made by Rajiv Murali HeriotWatt University Learning Outline Setting up Eclipse Simple HelloWorld program Basic ObjectOriented Programming Concept ID: 648637
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Slide1
Object-Oriented programming for BeginnersLEAPS Computing 2015
Ioannis
Efstathiou
ie24@hw.ac.uk
(slides originally made by Rajiv
Murali)
Heriot-Watt
UniversitySlide2
Learning Outline
Setting up Eclipse
Simple HelloWorld program.
Basic Object-Oriented Programming Concept
What is an Object?
What is a Class?
Language Basics
Variables
Operators
Expressions, Statements and Blocks
Control Flow Statements
Conditional Statements,Loop statements
MethodsSlide3
Simple Eclipse Start-UpSlide4
Creating a Java Project in Eclipse IDE
Step 1: Start Eclipse
Step 2: Click File > New > Java Project
Step 3: Enter a Project name, e.g. “JavaTutorial”, and click “Finish”.
Step 4: Right-click on the project folder and select New > Class.
Step 5: Enter “HelloWorldDemo” as the name, and click “Finish”.
Step 6: Edit the HelloWorldDemo.class file as follows:
public class HelloWorldDemo {
public static void main(String args[ ]) {
System.out.println("Hello World!");
}
}
Step 7: Run the HelloWorldDemo.class.Slide5
Assignment HelloWorld
In this assignment I want you to use the HelloWorldDemo Class to:
output the following message
: “Hello World! my name is #your name here#!”Slide6
Object-Oriented ProgrammingSlide7
Object-Oriented Programming
Java is an Object-Oriented Programming Language.
Before you begin writing Java code, you will need to learn a few basic object-oriented concepts.
This lesson will introduce you to:
what is an Object?
what is a Class?
To help better understand these concepts, we will relate them to examples Java code that you will run in your
Eclipse IDE.Slide8
What is an Object?
Look around right now and you'll find many examples of real-world
objects
:
your desk, your books, your computers and even yourselves.
Objects share two characteristics: State and Behaviour.
For example an object Person may have:
state - name, age, weight, etc.
behavior - walking, eating, sleeping, etc.
Take a minute and think of some examples of Objects around you, with some state and behaviour.Slide9
Objects in Software
Similar to real-world objects, software objects also consist of state and behaviour.
A software object stores its...
states in fields, also known as
variables
in most programming languages.
while its behaviour is exposed through
methods
.
an Object -
Student
eating
sleeping
walking
name
age
weight
Methods help to operate an object's internal state.Slide10
What is a Class?
Often there are many individual objects of the same kind.
There are billions of people in existence, and all people fall under the kind human.
A Class helps to capture the common features of objects.
And from a Class, many instances of Objects may be created.
In object-oriented terms, we say that an Object person is an instance of a Class Human.Slide11
What does Class Human look like in code?
class Human {
int age;
string name;
void increaseAge() {
age++;
}
void setNameandAge(String parameterName, int parameterAge) {
name = parameterName;
age = parameterAge;
}
void printHumanInfo() {
System.out.println(“Name: ”+ name);
System.out.println(“Age: ” +age);
}
}
Class
Field / Variable
MethodsSlide12
Creating an object from Human Class…
We want to create a person from our human class...
But the Human class is not a complete application!
It does not contain a
main
method.
The responsibility of creating and using people from the human class belongs to another application….Slide13
HumanDemo Class
class HumanDemo {
public static void main(String[] args){
Human frank = new Human();
frank.setNameandAge(“Frank”, 10);
frank.printHumanInfo();
}
}
The HumanDemo Class helps creates an instance frank of the Human class. We then set the name and age of Frank to 10.
Program Execution
Creates an instance frank from the Human Class.
Sets the name and age of frank.
Prints the information of frank.Slide14
Assignment HumanDemo
In this assignment I want you to use the HumanDemo Class to:
1. Set the age of frank to 100.
2. Set the name of frank to “Frankenstein”.
3. Print the
current
information.
4. Then increase Franks age by 3.
5. And finally, print the information again.