Скачать или смотреть How to Create a Class Constructor in Java that Accepts Another Class as Input Professor(Professor)

Learn how to create a constructor in Java that allows you to instantiate a class using another instance of that same class as an argument.
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This video is based on the question https://stackoverflow.com/q/63836403/ asked by the user 'Rancio' ( https://stackoverflow.com/u/9728923/ ) and on the answer https://stackoverflow.com/a/63836481/ provided by the user 'k1r0' ( https://stackoverflow.com/u/3364146/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Create a Class Constructor in Java that Accepts Another Class as Input Professor(Professor)

When working in Java, you might find yourself in a situation where you need to create a constructor that accepts another instance of the same class as a parameter. This scenario often arises in object-oriented programming when you're aiming for cleaner and more intuitive code. Let's explore how we can achieve this using the Professor class as an example.

The Problem

You have a Professor class that serves as a blueprint for creating professor objects. The current constructor for the Professor class takes different attributes like name, surname, year of birth, and department. However, in your tests, you may need to create a new Professor instance using an existing one. The challenge is to create a constructor that allows you to pass an instance of Professor as a parameter.

Here’s the current structure of your class:

[[See Video to Reveal this Text or Code Snippet]]

Current Constructor Implementation

Your current constructor signature allows for the creation of a Professor object as follows:

[[See Video to Reveal this Text or Code Snippet]]

However, how do you call this constructor when you have another instance of Professor available?

The Solution

The solution lies in creating an additional constructor within the Professor class that accepts a Professor object as its parameter. This "copy constructor" can streamline the instantiation process by calling one of the existing constructors. Below, I’ll break down how to implement this effectively.

Step 1: Define the Copy Constructor

You need to define a new constructor in your Professor class that takes an instance of Professor. This copy constructor will delegate to the existing constructor that takes individual attributes:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Full Implementation Example

Here’s how your complete Professor class could look including all necessary constructors:

[[See Video to Reveal this Text or Code Snippet]]

How It Works

Now, you have three constructors in the Professor class:

Constructor that takes name, surname, and year of birth: This is for basic object creation.

Constructor that takes all attributes including the department: This is for fully populated Professor objects.

Copy constructor: This allows you to create a new Professor instance using an existing one, which is particularly useful in testing scenarios.

Example Usage

You can now create a new Professor instance using an existing one like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Creating a constructor that accepts another instance of the same class is not only straightforward but also beneficial in maintaining clean and efficient code. Using Java’s feature of constructor overloading makes this possible, allowing for a flexible object-oriented approach. The copy constructor enhances your ability to manage object states effectively, especially during testing and object duplication scenarios.

With this knowledge, you can now implement similar patterns in other classes as needed. Happy coding!