What Is Constructor Overloading in Java? (Java Interview QA)

Learn what constructor overloading is in Java, why it’s useful, and how to implement it with real-world examples and simple explanations.

📌 Definition

Constructor overloading in Java means creating multiple constructors in the same class, each with different parameter lists.

➡️ It allows you to create objects in multiple ways depending on what data is available.

🧱 Basic Syntax

public class Book {
    String title;
    String author;

    // Constructor 1
    public Book() {
        this.title = "Unknown";
        this.author = "Unknown";
    }

    // Constructor 2
    public Book(String title) {
        this.title = title;
        this.author = "Unknown";
    }

    // Constructor 3
    public Book(String title, String author) {
        this.title = title;
        this.author = author;
    }
}

🧪 Usage:

Book b1 = new Book();                     // uses constructor 1
Book b2 = new Book("Java in Action");     // uses constructor 2
Book b3 = new Book("Spring Boot", "John"); // uses constructor 3

✅ Each constructor initializes the object differently based on the provided parameters.

Why Use Constructor Overloading?