The main difference between Class and Object is that a class is a blueprint or a template to create objects while an object is an instance of a class.
A programming paradigm denotes the style of organizing the structure and the elements of a computer program. One major paradigm is Object Oriented Programming (OOP). It allows the developers to model real-world scenarios easily. Furthermore, this paradigm allows creating software using objects. Class and object are two concepts related to OOP.
Key Areas Covered
1. What is Class
– Definition, Functionality
2. What is Object
– Definition, Functionality
3. Difference Between Class and Object
– Comparison of key differences
Key Terms
Attribute, Class, Constructor, Object, Method, OOP
What is Class
A class is a blueprint to create an object. It is a logical entity that provides the structure to create objects. In other words, the programmer can create multiple objects using one class. A class consists of attributes and methods. The attributes are the fields or methods. Methods describe the behaviors. Furthermore, a class can also contain a constructor. It is a special method that is used to initialize an object.
These attributes and methods of a class are called the members of the class. These members can have public, private or protected visibility. The public members are accessible outside the class while the private members are accessible only within the class. Moreover, the protected members are visible within the class and subclasses. The programmer can secure the attributes of a class by declaring them as private and allow accessing them using public methods.
What is Object
An object is an instance of a class. In other words, objects are created using a class. An object is an entity that has state and behaviors. The attributes of the class describe the state of an object. Similarly, the methods of a class describe the behaviors of an object.
For example, assume a medical management system. It has states such as name of the medical center, location, number of doctors, patients, etc. It also has behaviors or functionalities such as admitting patients, issue medical reports, enter doctor details, etc. Moreover, a banking system has states such as name of the bank, location, country, etc. while it has behaviors or functionalities such as deposit, withdraw, transfer money.
Likewise, using this class – object scenario, it is possible to model any real-world situation easily.
Figure 1: Java program with class and objects
In the above program, there is a class called Student. It has private properties called id, name, and gpa. The Student constructor helps to give initial values to these properties. There is a method called displayDetails to display the properties. In the main program, the student objects (s1, s2) are created. The new keyword helps to allocate memory for the objects at runtime. Then the dispalyDetails method is called using those objects. Therefore, the student details display on the console.
Difference Between Class and Object
Definition
A class is a template for creating or instantiating objects within a program while an object is an instance of a class. Thus, this is the main difference between Class and Object.
Type
Also, an important difference between Class and Object is that Class is a logical entity while Object is a physical entity.
Creation
Moreover, Class is declared with the “class” keyword whereas an object is created using the “new” keyword.
Memory allocation
A class does not get any memory when it is created whereas objects get memory when they are created. Hence, this is another difference between Class and Object.
Quantity
Furthermore, a class is declared once while multiple objects are created using a class.
Conclusion
Entire OOP is based on the concept of class and object. The main difference between Class and Object is that Class is a blueprint or a template to create objects while an object is an instance of a class. In brief, there should be a class to create objects.
References:
1.“Object in Java | Class in Java – Javatpoint.” Www.javatpoint.com, Available here.
2.“Class.” Class Definition, Available here.
Leave a Reply