the relationship between class and object in Java

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  1. In Java, and in object-oriented programming in general, classes and objects are fundamental concepts that are closely related but distinct.

    1. Class: A class in Java is a blueprint or a template from which objects are created. It defines a data structure that encapsulates data (attributes or properties) and methods (functions or behaviors). Think of a class as a sketch or prototype that defines the characteristics and behaviors (like speed, color, and turnOn(), turnOff() methods for a car) that the objects created from it will have.

      Example:

      public class Car {
          // Attributes of a car
          String color;
          int speed;
      
          // Method of a car
          void turnOn() {
              // Code to turn on the car
          }
      }
      
    2. Object: An object is an instance of a class. When a class is used to create an object, it's like creating a specific item from the blueprint. An object contains real values instead of the placeholder values that are present in a class. Continuing with the car analogy, if 'Car' is a class, then a specific car like 'myCar' with a specific color and speed is an object.

      Example:

      public class Main {
          public static void main(String[] args) {
              // Creating an object of the Car class
              Car myCar = new Car();
              myCar.color = "Red";
              myCar.speed = 100;
      
              // Calling a method of the Car class using myCar object
              myCar.turnOn();
          }
      }
      

    In summary:

    • A class is a template for objects.
    • An object is an instance of a class.
    • Each object has its own identity, state, and behavior, which are defined by the class.

    This relationship is critical in understanding object-oriented programming as it allows for the creation of multiple objects with the same properties and behaviors (as defined in the class) but with their own individual states.

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