A presentation on creating your first "Hello World" Java app and explanations on object-oriented paradigms

1. Introduction to Java
and object-oriented programming

2. Bina Nusantara Kemanggisan
Let’s print “Hello World”
Hello World!

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All you need to do is type System.out.println(“Hello World”);
Hello World!

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Make an incrementing line (i.e. 0 1 2 3 4 5 6 7 8 9)
Loops?

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To loop use, for(int i=0; i<10; i++) System.out.println(i+” “);
Loops?

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Let’s start learning
object-oriented

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Code using the concept of “objects”, implementing this paradigm is called
object-oriented programming
Object-oriented?

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Code using the concept of “objects”, implementing this paradigm is called
object-oriented programming
Object-oriented?

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Each object has its’ own attributes and functions. A constructor is usually made
to initialize the creation of an object.
Object-oriented?

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1. Make classes, lots of classes!
2. Set class attributes.
3. Make a constructor!
Implementation

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Encapsulation is used for information hiding.
Psstt… you don’t want your data being public! (it’s dangerous)
Encapsulation

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There are 3 types of encapsulation:
public, protected and private
Encapsulation

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Attributes that are public can be accessed by any class.
Attributes that are protected can only be accessed by child classes.
Attributes that are private can only be accessed by the class itself!
Encapsulation

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Easy! Just add public, protected or private in front of your attribute / function
i.e. private int price;
Implementation

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Inheritance is used to make a child class inherit attributes of its’ parent class
Inheritance

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Two important terms to remember for inheritance is parent and child
Inheritance

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A child has all the attributes and functions of its parents (not the other way around)
Inheritance

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In Java inheritance can be implemented by using extends
i.e. public class Hatchback extends Car
In the example above, it means the class Hatchback is a child of the Car parent class.
Implementation

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Polymorphism means “multiple forms”, essentially that is a literal
definition of polymorphism in object-oriented programming
Polymorphism

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Polymorphism has variant implementations
Polymorphism

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1. Referencing (having multiple inheritance thus making it polymorphic)
2. Virtual Methods (overriding parent class methods)
Implementation

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Oh… one more thing
overloading functions

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Overloading functions are functions with the same name but have
different formal parameters
Overloading Functions

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public int a(){
//functionstuff
}
public int a(int x){
//functionstuff
}
Implementation
This is an example of a overloading function. In
this example, function a could receive two types of
parameters none or when an integer is passed.
Thus we can choose to implement a certain
function by passing different parameters.

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1. Tutorials Point: Java - Encapsulation
https://www.tutorialspoint.com/java/java_encapsulation.htm
2. Tutorials Point: Java - Inheritance
https://www.tutorialspoint.com/java/java_inheritance.htm
3. Tutorials Point: Java - Polymorphism
https://www.tutorialspoint.com/java/java_polymorphism.htm
Study Reference

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and we’re done!