programming-classes-objects-methods-and-attributes

Programming Classes

• To program classes, you should already have a solid understanding of what classes in Object Oriented Programming (OOP) are.

How do you Define a Class?

In this example we will:

• Define a class for a car sales program where the following is required:

  • Name of Manufacturer

  • Model of Car

  • Price

  • Mileage

  • Whether the car is preowned

• Instantiate two objects for the car sales program ensuring that they have appropriate identifiers

• List two methods that would be useful for a car object

Pseudocode

Pseudocode for creating classes, a constructor, and functions

Java

//creating a class called cars

public class Cars {

//creating class attributes for a car

private String Manufacturer;

private String Model;

private int Price;

private int Mileage;

private boolean PreOwned;

//Constructor - This is used to create the objects. More on this in the object chapter)

public Cars(String manufacturer, String model, int price, int mileage, boolean preOwned) {

this.Manufacturer = manufacturer;

this.Model = model;

this.Price = price;

this.Mileage = mileage;

this.PreOwned = preOwned;

}

//method to make the car go faster.

public void Accelerate(){

//code to be executed which will make the car go faster

}

//Method to honk horn

public void honkHorn(){

// code to be executed which will honk the car horn

}

}

Python

#creating a class called cars

class Cars:

# constructor - This is used to create the objects. More on this in the object chapter)

def __init__(self, manufacturer, model, price, mileage, preOwned):

self.Manufacturer = manufacturer

self.Model = model

self.Price = price

self.Mileage = mileage

self.PreOwned = preOwned

#method to make the car go faster.

def Accelerate(self):

# code to be executed which will make the car go faster

 

# method to honk horn

def honkHorn(self):

# code to be executed which will honk the car horn

Programming Objects

• To program objects, you should already have a solid understanding of what objects in Object Oriented Programming (OOP) are.

Defining an Object

Pseudocode

Pseudocode for the class ‘person’ and instantiating two objects

Java

//creating the person class

public class Person {

// creating 4 attributes for the person class

private String firstName;

private String surname;

private String dateOfBirth;

private String hobbies;

 

// Constructor -This creates objects of the person class

public Person(String firstName, String surname, String dateOfBirth, String hobbies) {

this.firstName = firstName;

this.surname = surname;

this.dateOfBirth = dateOfBirth;

this.hobbies = hobbies;

}

//Creating Objects (Instances) of the person class

Person person1 = new Person("Bob", "Jones", "06/10/1981", “E Sports”);

Person person2 = new Person("Jess", "Jones", "05/04/1980", “Astronomy”);

Python

#creating the person class

class Person:

#Constructor -This creates objects of the person class

def __init__(self, firstName, surname, dateOfBirth, hobbies):

self.firstName = firstName

self.surname = surname

self.dateOfBirth = dateOfBirth

self.hobbies = hobbies

 

#Creating Objects (Instances) of the person class

person1 = Person("Bob", "Jones", "06/10/1981", "E Sports")

person2 = Person("Jess", "Jones", "05/04/1980", "Astronomy")

Programming Methods

• To program methods, you should already have a solid understanding of what methods in Object Oriented Programming (OOP) are.

Defining Methods

Pseudocode

Pseudocode for creating methods

 

Java

//Creating a public method called BankLeft

public void bankLeft() {

 // Code to make the aircraft bank left

}

//Creating a private Method called BankLeft

public void bankLeft() {

 // Code to make the aircraft bank left

}

Python

#Creating a public method called BankLeft

def bank_left(self):

# Code to make the aircraft bank left

#Creating a private method called BankLeft

• In Python, there is no explicit access modifier for methods like “private” in Java.

• By convention, methods with a single leading underscore _ are considered private and should not be accessed directly from outside the class.

_def _bank_left(self):

# Code to make the aircraft bank left

• It’s important to note that even though the method is marked as private, it can still be accessed and invoked from outside the class. However, as a rule, other developers should treat it as private and avoid accessing it directly.

Programming Attributes

Pseudocode

Example of a created class, “Person”, containing several attributes

Java 

public class Person {

// Attributes for the person class

private String name;

private int age;

private String gender;

private String occupation;

private boolean isMarried;

}

Python

In Python attributes are defined using the self keyword followed by the attribute name and its initial value.

class MyClass:

def __init__(self, attribute1, attribute2):

# Define attributes

self.attribute1 = attribute1

self.attribute2 = attribute2