What is a Copy Constructor?

A copy constructor allows you to create a new object as a copy of an existing object. This is particularly useful when you want to duplicate an object with the same state as another. In Java, copy constructors are user-defined since the language does not provide a default copy constructor.

• Characteristics:
  • Takes an object of the same class as a parameter.
  • Copies the values of the member variables from the passed object to the new object.
  • Ensures that the new object has the same state as the original object.

Syntax of a Copy Constructor

class ClassName {
    // Copy constructor
    ClassName(ClassName other) {
        // Initialization code
    }
}

Explanation:

• ClassName(ClassName other): The constructor takes another object of the same class (other) as a parameter.
• Initialization code: Assigns the values of the member variables from other to the new object being created.

Example 1: Car Class with Copy Constructor

In this example, we define a Car class with a copy constructor that initializes a new Car object using the state of an existing Car object.

Explanation:

• Car(Car other):
  This is the copy constructor for the Car class. It takes another Car object (other) as a parameter.

• this.brand = other.brand;, this.color = other.color;, this.year = other.year;:
  These lines copy the values of brand, color, and year from the other object to the new Car object.

• Car copiedCar = new Car(originalCar);:
  Creates a new Car object copiedCar by copying the state of originalCar using the copy constructor.

A copy constructor enables the creation of a new object as an exact copy of an existing object. Unlike assignment, which copies references, the copy constructor duplicates the actual data, ensuring that the new object has the same state as the original.

In this lesson, we explored the syntax and usage of copy constructors using the Car and Animal class examples. We demonstrated how to define copy constructors, create new objects using them, and understand the significance of copying object states accurately.