Meta Class Vs. Class in Java

In any object-oriented programming language, a meta class can be defined as a class which is utilized in defining the behaviour of various other classes. In Java, a class can be defined as a constructor of an object which is utilized for the creation of objects. In simple words, a class can be considered as a blueprint in Java.

Let's understand about Meta class and Classes in Java in detail.

Meta Class

In various object-oriented programming language, a Meta class can be simply defined as a type of class which is majorly utilized for the purpose of defining the functionality and behaviour of various other classes. A regular class in programming language is mainly utilized for defining the blueprint that gets used for creation of objects. But however, a Meta class is utilized for the purpose of defining how the classes are created themselves.

In programming languages such as Python, the default type of Meta class is considered as the "type" Meta class. Similarly, in Python custom meta classes could be created by developers for exerting control over the process of class creation.

It is very important to understand that although Meta classes give robust customization features and functionalities, they are termed and considered as advanced and powerful features and they should be used and implemented accordingly. Excessive usage of Meta classes often leads to creation of code that becomes very difficult and complex for understanding and maintenance.

In short words, Meta class plays an important role in object-oriented programming languages for the purpose of controlling the creation and control of classes. Developers are allowed the features and functionalities for implementing custom logics that get implemented during the creation process of a class. However, Meta classes must be implemented and utilized with utmost care and precaution.

Let us understand about classes in Java in detail in the following paragraphs.

Classes in Java

In Java programming language, a class can be defined as a necessary building block that is related to object-oriented programming (OOP) principles. In other words, a class can be considered as a blueprint or a temple that is mainly utilized for defining the attributes, fields, class members or variables, methods, etc. The class can be declared in a Java program with the help of a syntax that is carried out by the class keyword which is followed by the name of the class.

Let's understand about classes in Java in detail with the help of a Java example program.

Filename: JavaClasses.java

// Java program for demonstrating the features and functionalities of Classes in Java.
interface Display {
    void display();
}
abstract class Shape implements Display {
    protected String color;
    public Shape(String color) {
        this.color = color;
    }
    // Abstract method that should be implemented by subclasses
    public abstract double calculate_Area();
    // Getter
    public String get_Color() {
        return color;
    }
    // Setter
    public void set_Color(String color) {
        this.color = color;
    }
}
// Class representing a circle
class Circle extends Shape {
    private double radius;
    public Circle(String color, double radius) {
        super(color);
        this.radius = radius;
    }
    // Implemented method from the Shape abstract class
    @Override
    public double calculate_Area() {
        return Math.PI * Math.pow(radius, 2);
    }
    // Implemented method from the Display interface
    @Override
    public void display() {
        System.out.println("Drawing a circle with color " + color);
    }
    public double get_Radius() {
        return radius;
    }
    // Setter for radius
    public void set_Radius(double radius) {
        this.radius = radius;
    }
}
// Class representing a rectangle
class Rectangle extends Shape {
    private double length;
    private double width;
    public Rectangle(String color, double length, double width) {
        super(color);
        this.length = length;
        this.width = width;
    }
    // Implemented method from the Shape abstract class
    @Override
    public double calculate_Area() {
        return length * width;
    }
    // Implemented method from the Display interface
    @Override
    public void display() {
        System.out.println("Drawing a rectangle with color " + color);
    }
    // Additional methods
    public double get_Length() {
        return length;
    }
    public double get_Width() {
        return width;
    }
    // Setters for length and width
    public void set_Length(double length) {
        this.length = length;
    }
    public void set_Width(double width) {
        this.width = width;
    }
}
public class JavaClasses{
    public static void main(String[] args) {
        Circle redCircle = new Circle("Red", 5.0);
        Rectangle blueRectangle = new Rectangle("Blue", 4.0, 6.0);
        Display[] displayables = { redCircle, blueRectangle };
        for (Display displayable : displayables) {
            displayable.display();
        }
        System.out.println("Area of Red Circle: " + redCircle.calculate_Area());
        System.out.println("Area of Blue Rectangle: " + blueRectangle.calculate_Area());
        System.out.println("Color of Red Circle: " + redCircle.get_Color());
        System.out.println("Length of Blue Rectangle: " + blueRectangle.get_Length());
        redCircle.set_Color("Crimson");
        blueRectangle.set_Length(5.0);
        System.out.println("Updated Color of Red Circle: " + redCircle.get_Color());
        System.out.println("Updated Length of Blue Rectangle: " + blueRectangle.get_Length());
    }
}

Output:

Drawing a circle with color Red
Drawing a rectangle with color Blue
Area of Red Circle: 78.53981633974483
Area of Blue Rectangle: 24.0
Color of Red Circle: Red
Length of Blue Rectangle: 4.0
Updated Color of Red Circle: Crimson
Updated Length of Blue Rectangle: 5.0

Differences Between Meta class and Class in Java

The features and functionalities of Meta class are found in object-oriented programming languages. But it is important to note that the features of Meta class are not supported and provided in the Java programming language, but instead they are supported and provided in the Python programming language.
In Java programming language, a class can be defined as a necessary building block that is related to object-oriented programming (OOP) principles. In other words, a class can be considered as a blueprint or a temple that is mainly utilized for defining the attributes, fields, class members or variables, methods, etc. On the other hand, a Meta class can be simply defined as a type of class which is majorly utilized for the purpose of defining the functionality and behaviour of various other classes.
Metaclass is majorly utilized for defining the controlling the behaviours of other classes. But unfortunately, there is no equivalent of metaclass found in Java programming language. However, reflection is a feature that is supported and provided in Java that lets developers inspect and manipulate the classes, methods, fields and other members of Java.
In conclusion, classes in Java can be considered as building or fundamental blocks that are utilized for the creation of objects and they act as a blueprint. Whereas, the concepts of metaclass are not supported and provided in Java, several features such as reflection are utilized for dynamically inspecting and manipulating classes during the runtime execution.

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