Tag: Concepts

Some other concepts

--Originally published at chozaoop

Happy Valentine’s Day!

So in this post i’m gonna share the remaining OOP theoric concepts that will be featuring in partial #1 exam. Mentioning them and then referencing the source, if you like the explanations and would like to copy them you are free to do so, if you have a comment, leave a comment please, ya know, Ken likes discussion.

Abstraction

What is abstraction?

Abstraction is process of hiding the implementation details and showing only the functionality. Is used to hide certain details and only show the essential features of the object.

You implement it like this:

“abstract class <class-name>”as creating an abstract class

and as for a method “abstract public void <method-name>;”

This concept kinda relates to encapsulation, since encapsulation means hiding information inside the object, while abstraction deals with the outside or the interface.

Encapsulation = Object Internally —–Abstraction = Object Externally

An Abstact Class cannot be instanciated, and an Abstract method is a method which is declared without implementation.

An Abstract class and a Final Class have the opposite meaning.

When do i use it? When i know that i need to implement something, but not exactly what it is or how it should look like.

S O U R C E

Java Visibility Modifiers

            | Class | Package | Subclass | World
————————————+———————+—————————+——————————+———————
public      |  y    |    y    |    y     |   y
————————————+———————+—————————+——————————+———————
protected   |  y    |    y    |    y     |   n
————————————+———————+—————————+——————————+———————
no modifier |  y    |    y    |    n     |   n
————————————+———————+—————————+——————————+———————
private     |  y    |    n    |    n     |   n

y: accessible
n: not accessible

Really nice table.

Default: This one might be a mistake, it means adding no access modifier. As you can see on the table, only available this class or a class in the same package, it is not available for subclasses or the rest of the world.

Public: Available anywhere, any other class, subclass or even any class in the world, this one provides the most access while private provides the least.

Protected: I see this one as using the class inside your own works, i mean if you create a package and a class and then a subclass, protected modifier keeps any foreign intruder away, but still making it available for you.

Private: PRIVATE EYES! This modifier only allows access from the same class, no other package, subclass and obviously the rest of the world.

So remember:

Public > Protected > No Modifier > Private.

From most access to least.

Ok so the purpose of using these modifiers is, well, controlling the access to your member variables and functions, whether it is in your own program or most importantly, the outside world.

We do give it a use sometimes in this course but it’s really really important to know how to use these when making a big project since you never know who wants to mess up your stuff and if you know how to use modifiers it should keep you safe.

SO UR CE


Some other concepts

Basic OOP concepts

--Originally published at tc2016blog

Since I didn’t make this post before, here it is.

I’ll be defining the four most basic concepts of Object-Oriented Programming (OOP) With a common acronym used by the OOP community APIE.

This acronym stands for Abstraction, Polymorphism, Inheritance and Encapsulation.

Inheritance is used to stop the code copy-pasting, by this I mean that if you have a class (e.g. Animal) which has certain attributes and methods you could use in another class (e.g. Dog), you should make the second class Dog inherit from the first class Animal, making them child and parent, or superclass and subclass, respectively. To do this we use the extends keyword after the subclass identifier and we write the superclass right besides it.

   public class Dog extends Animal{
}

For example, I have an Animal class which has color and name attributes and a toWalk method, and want to create another class named Dog; instead of repeating the code to instantiate the color and name attributes and the toWalk method, I make it a subclass of Animal, so now Dog has all the attributes and methods Animal has by default.

Abstraction is similar to Inheritance, but in this case abstraction has a little bit more “power” if you’d like. By “power” I mean that an abstract class has the ability to choose which method any subclass HAS to use in order work correctly. In order to do this you should start by defining the class as an abstract class.

Encapsulation is to keep everything in one place, which is done with the different level modifiers public, private, protected and default. This is useful to avoid any variables being changed by any other actor aside from the class which instantiated them in the first place.

For example, in this WSQ I made:

Basic OOP concepts

As you can see I instantiated the int myNumber as private so only that class has modifying access to it and the GCD class can’t change it.

Polymorphism is the hardest one, the word, by etymology, means many forms, and in programming context it means that “classes have different functionality while sharing the same interface”.

Let me explain, this is closely related to Inheritance, this means that while a class can be used for many different functions, it can also be overridden for it to change its functionality and be more suitable for different applications. By overriding I mean literally overriding superclass’s methods in the subclass in order to return a different value or do a completely different thing, this is implemented in code with and override keyword while re-defining the method.

public class theExample extends PolyExample{
public override int randomMethod{
return 5;
}
}

Hope I helped, this was a long post, and hard one for Polymorphism, since I first had to really understand the concept in order to make the post more suitable for everyone.

References:

http://www.jakowicz.com/what-is-apie/

http://stackoverflow.com/questions/1031273/what-is-polymorphism-what-is-it-for-and-how-is-it-used

 


Basic OOP concepts

Basic OOP concepts

--Originally published at tc2016blog

Since I didn’t make this post before, here it is.

I’ll be defining the four most basic concepts of Object-Oriented Programming (OOP) With a common acronym used by the OOP community APIE.

This acronym stands for Abstraction, Polymorphism, Inheritance and Encapsulation.

Inheritance is used to stop the code copy-pasting, by this I mean that if you have a class (e.g. Animal) which has certain attributes and methods you could use in another class (e.g. Dog), you should make the second class Dog inherit from the first class Animal, making them child and parent, or superclass and subclass, respectively. To do this we use the extends keyword after the subclass identifier and we write the superclass right besides it.

   public class Dog extends Animal{
}

For example, I have an Animal class which has color and name attributes and a toWalk method, and want to create another class named Dog; instead of repeating the code to instantiate the color and name attributes and the toWalk method, I make it a subclass of Animal, so now Dog has all the attributes and methods Animal has by default.

Abstraction is similar to Inheritance, but in this case abstraction has a little bit more “power” if you’d like. By “power” I mean that an abstract class has the ability to choose which method any subclass HAS to use in order work correctly. In order to do this you should start by defining the class as an abstract class.

Encapsulation is to keep everything in one place, which is done with the different level modifiers public, private, protected and default. This is useful to avoid any variables being changed by any other actor aside from the class which instantiated them in the first place.

For example, in this WSQ I made:

Basic OOP concepts

As you can see I instantiated the int myNumber as private so only that class has modifying access to it and the GCD class can’t change it.

Polymorphism is the hardest one, the word, by etymology, means many forms, and in programming context it means that “classes have different functionality while sharing the same interface”.

Let me explain, this is closely related to Inheritance, this means that while a class can be used for many different functions, it can also be overridden for it to change its functionality and be more suitable for different applications. By overriding I mean literally overriding superclass’s methods in the subclass in order to return a different value or do a completely different thing, this is implemented in code with and override keyword while re-defining the method.

public class theExample extends PolyExample{
public override int randomMethod{
return 5;
}
}

Hope I helped, this was a long post, and hard one for Polymorphism, since I first had to really understand the concept in order to make the post more suitable for everyone.

References:

http://www.jakowicz.com/what-is-apie/

http://stackoverflow.com/questions/1031273/what-is-polymorphism-what-is-it-for-and-how-is-it-used

 


Basic OOP concepts