What will be the output of this program? Java class Demo { int num; Demo() { this(100); System.out.println("Default Constructor"); } Demo(int n) { num = n; System.out.println("Parameterized Constructor"); } } public class Main { public static void main(String[] args) { Demo obj = new Demo(); } }

Parameterized ConstructorDefault Constructor

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Java Constructors

Here are 10 essential multiple-choice questions on Java Constructors, covering key concepts.

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Question 1

Which of the following is true about Java constructors?

Constructors have a return type of void.
Constructors must always be public.
A constructor is automatically called when an object is created.
Constructors can only be defined explicitly.

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Question 2

What happens if you do not define a constructor in a Java class?

The program will not compile.
The compiler provides a default constructor.
The class cannot be instantiated.
The constructor from another class will be used.

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Question 3

What will be the output of the following Java code?

Java

class Test {
    int x;
    Test() {
        x = 10;
    }
}
public class Main {
    public static void main(String[] args) {
        Test obj = new Test();
        System.out.println(obj.x);
    }
}

Compilation error
0
10
Null

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Question 4

Can a Java constructor be private?

No, it must be public.
Yes, but the class cannot be instantiated outside the class.
Yes, and it can be accessed from anywhere.
No, Java does not allow private constructors.

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Question 5

How can one constructor call another constructor within the same class?

Using super()
Using this()
Using new()
Constructors cannot call each other

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Question 6

What will be the output of this program?

Java

class Demo {
    int num;
    Demo() {
        this(100);
        System.out.println("Default Constructor");
    }
    Demo(int n) {
        num = n;
        System.out.println("Parameterized Constructor");
    }
}
public class Main {
    public static void main(String[] args) {
        Demo obj = new Demo();
    }
}

Default Constructor
Parameterized Constructor
Parameterized Constructor
Default Constructor
Compilation Error

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Question 7

What will happen if you explicitly define a constructor with parameters but do not define a no-argument constructor?

Java will provide a default no-argument constructor.
You cannot create an object without passing arguments.
Compilation error occurs.
The constructor will be inherited from Object class.

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Question 8

Can a constructor be final in Java?

Yes, if you override it.
No, because constructors are not inherited.
Yes, but only in abstract classes.
Yes, but only for utility classes.

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Question 9

What will be the output of the following code?

Java

class Base {
    Base() {
        System.out.println("Base Constructor");
    }
}
class Derived extends Base {
    Derived() {
        System.out.println("Derived Constructor");
    }
}
public class Main {
    public static void main(String[] args) {
        Derived obj = new Derived();
    }
}

Base Constructor
Derived Constructor
Derived Constructor
Base Constructor
Compilation Error
Runtime Error

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Question 10

What will be the output of this program?

Java

class A {
    private A() {
        System.out.println("Private Constructor");
    }
    public static void createInstance() {
        new A();
    }
}
public class Main {
    public static void main(String[] args) {
        A.createInstance();
    }
}

Compilation Error
Private Constructor
Runtime Error
No Output

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