Class vs. Structure in Java

Class and Structure are both fundamental programming concepts used to organize and manage data. Although both are used to group data, there are several significant differences between them, mainly related to the principles of Object-Oriented Programming (OOP) and traditional programming languages. Note that Java does not have `struct` in the same way C/C++ does; Java uses classes for all structured data. This comparison is often made to understand the design philosophy of Java.

A class is a fundamental unit of Object-Oriented Programming (OOP). It is a blueprint for data and methods, which is used in the form of objects.

A class is a template that defines objects and specifies the properties and methods that the objects of that class will have. You can create many objects based on one class.

class Car {
    // Properties (data members)
    String color;
    String model;
    
    // Constructor
    Car(String c, String m) {
        color = c;
        model = m;
    }
    
    // Methods (functions)
    void displayInfo() {
        System.out.println("Car Model: " + model + ", Color: " + color);
    }
}

A structure is a data structure mainly used in programming languages like C and C++. In a structure, you can group different types of data, such as integer, float, character, etc. However, a structure typically only has data members and does not support functional methods.

A structure is a way to organize a group of data. It is specifically used for grouping data and generally lacks OOP features.

// Example in C/C++
struct Car {
    // Data members
    char color[20];
    char model[20];
};

A class fully supports all OOP concepts like inheritance, encapsulation, and polymorphism. This simplifies code reuse and maintenance.

In contrast, a structure does not support OOP features, especially in C. A structure is only for organizing data and is not designed from an OOP perspective.

In a class, we can use public, private, and protected access modifiers to control which members can be accessed from external code. This helps in securing the data within the class.

In a C structure, all members are public by default, meaning they can be accessed by any external code. Although C++ structures can use access modifiers, they are generally used just for organizing data.

A class has constructors and destructors, which control special actions at the time of object creation and destruction. This helps in initializing and finalizing the state of an object.

A structure, especially in C, does not have such features, so data must be initialized manually.

A class supports inheritance, allowing one class to inherit properties from another. This allows for code reuse and makes the program modular.

A structure in C does not have inheritance, so it is not considered suitable for reuse.

Memory for class objects is allocated on the heap, making it suitable for large data structures. Memory for structures (in C/C++) is often allocated on the stack, which is suitable for small data structures.