Interview on Constructors in Java : Key Questions and Answers

Interviewer : Welcome! Let’s start with the basics. Can you explain what a constructor is in Java ?

Candidate : Absolutely. A constructor in Java is a special method used to initialize objects. It has the same name as the class and does not have a return type, not even void. Constructors are called automatically when an instance of a class is created, and they are typically used to set initial values for object attributes or to perform any setup steps needed when an object is created.

class MyClass {
    int value;

    // Constructor
    MyClass() {
        value = 10;
    }
}

Interviewer : Great! Can you differentiate between a default constructor and a parameterized constructor?

Candidate: Sure. A default constructor is a no-argument constructor that is automatically provided by the Java compiler if no other constructors are defined in a class. This constructor does nothing beyond object creation.

On the other hand, a parameterized constructor takes arguments and allows you to initialize an object with specific values. If a class defines any constructors, the default constructor is not provided by the compiler.

class MyClass {
    int value;

    // Default constructor
    MyClass() {
        value = 10;
    }

    // Parameterized constructor
    MyClass(int val) {
        value = val;
    }
}