Java Classes/Objects

Java Classes and Objects

In Java, classes and objects are like the building blocks of your program. They help you organize your code and represent real-world things. In this tutorial, we'll break down what classes and objects are in Java.

Classes:

• Imagine a class as a blueprint or a template.
• It defines the structure or characteristics of an object.
• Just like a blueprint for a house tells you how to build a house, a class tells you how to create an object.

Objects:

• Think of an object as something real and tangible.
• It's like a specific instance of a class.
• For example, if the class is "Car," an object could be "MyCar," which has its own unique features like color, model, and speed.

Creating a Class:

To create a class, use the keyword class

class CarBlueprint {
    String make;
    String model;
    int year;
}

CarBlueprint myCar = new CarBlueprint();

Creating Objects from Classes:

• To create an object for a class , specify the class name, followed by the object name, and use the keyword new
• Each object is unique, like individual cars on the road.

CarBlueprint car1 = new CarBlueprint();
CarBlueprint car2 = new CarBlueprint();

Object Properties (Attributes):

• Objects have characteristics called attributes.
• These attributes are like the details of a car, such as make, model, and year.

car1.make = "Toyota";
car1.model = "Camry";
car1.year = 2022;

Object Behaviors (Methods):

• Objects can perform actions called methods.
• It's like a car can "start" or "stop."

class CarBlueprint {
    void start() {
        System.out.println("Car is starting...");
    }
}

CarBlueprint myCar = new CarBlueprint();
myCar.start(); // Output: Car is starting...

Accessing Object Attributes:

• To access an object's attributes, use the dot notation (object.attribute).
• It's like reading a book's title from its cover.

class Book {
    String title;
}

Book myBook = new Book();
myBook.title = "Java Programming";

// Accessing attribute
String bookTitle = myBook.title;
System.out.println("Title: " + bookTitle); // Output: Title: Java Programming

Modifying Object Attributes:

• You can change an object's attribute by assigning a new value using the dot notation.
• It's like updating a book's title on its cover.

class Book {
    String title;
}

Book myBook = new Book();
myBook.title = "Java Programming";

// Modifying attribute
myBook.title = "Java Mastery";
System.out.println("New Title: " + myBook.title); // Output: New Title: Java Mastery

Invoking Object Methods:

• To use an object's method, call it using the dot notation (object.method()).
• It's like following a recipe to cook a dish.

class Calculator {
    int add(int a, int b) {
        return a + b;
    }
}

Calculator myCalculator = new Calculator();

// Invoking method
int sum = myCalculator.add(5, 7);
System.out.println("Sum: " + sum); // Output: Sum: 12

Modifying Object Methods:

• You can't directly modify object methods, but you can extend or override them in a subclass.
• t's like customizing a recipe to create a unique dish.

class Bird {
    void sing() {
        System.out.println("Bird is singing...");
    }
}

class Parrot extends Bird {
    void sing() {
        System.out.println("Parrot is singing loudly!");
    }
}

Bird myBird = new Parrot();

// Invoking method
myBird.sing(); // Output: Parrot is singing loudly!