Java OOPs Concepts Test 3

    Question 1: JAVA OOPS - Object Creation Syntax

    Which statement is invalid?

    class Car {}

    Question 2: JAVA OOPS - `this()` Keyword in Constructor

    What will the following code print?

    class Test {
    Test() { System.out.println("Default"); }
    Test(int x) { this(); System.out.println(x); }
}
public class Main {
    public static void main(String[] args) {
        Test t = new Test(5);
    }
}

    Question 3: JAVA OOPS - super Keyword

    Which statement is true about super keyword?

    Question 4: JAVA OOPS - `super` in Runtime Polymorphism

    What will be printed?

    class A { void show() { System.out.println("Parent"); } }
class B extends A {
    void show() {
        super.show();
        System.out.println("Child");
    }
}
public class Main {
    public static void main(String[] args) {
        B obj = new B();
        obj.show();
    }
}

    Question 5: JAVA OOPS - Interface vs Abstract Class

    Which is true about interface and abstract class?

    Question 6: JAVA OOPS - Write-only Property

    Which statement is correct?

    Question 7: JAVA OOPS - Interface Reference

    Which statement is correct?

    interface A { void show(); }
class B implements A { public void show() { System.out.println("Hi"); } }

    Question 8: JAVA OOPS - Accessing Classes in Package

    Which statement about access modifiers is correct for packages?

    Question 9: JAVA OOPS - Final Class

    Which statement is true about a final class?

    Question 10: JAVA OOPS - toString() Overriding

    What is the purpose of overriding toString() method?

    Question 11: JAVA OOPS - Class Member Access

    What will be the output?

    class A {
    int x = 10;
}
class B {
    int y = 20;
}
public class Main {
    public static void main(String[] args) {
        A a = new A();
        B b = new B();
        System.out.println(a.x + b.y);
    }
}

    Question 12: JAVA OOPS - Constructor Chaining

    Which concept is demonstrated here?

    class Demo {
    Demo() { System.out.println("A"); }
    Demo(int x) { this(); System.out.println("B"); }
}

    Question 13: JAVA OOPS - Multiple Inheritance

    Why is multiple inheritance not allowed with classes in Java?

    Question 14: JAVA OOPS - Polymorphism with Return Type

    Which is true about overriding and return types?

    Question 15: JAVA OOPS - Abstract Class Reference

    What will be printed?

    abstract class A {
    abstract void show();
    void display() { System.out.println("Display"); }
}
class B extends A {
    void show() { System.out.println("Show"); }
}
public class Main {
    public static void main(String[] args) {
        A obj = new B();
        obj.display();
    }
}

    Question 16: JAVA OOPS - Multiple Objects Encapsulation

    What will be printed?

    class Counter {
    private int count = 0;
    public void increment() { count++; }
    public int getCount() { return count; }
}
public class Main {
    public static void main(String[] args) {
        Counter c1 = new Counter();
        Counter c2 = new Counter();
        c1.increment();
        System.out.println(c2.getCount());
    }
}

    Question 17: JAVA OOPS - Interface with Variables

    Which of the following statements is true?

    Question 18: JAVA OOPS - Sub-package Access

    Which statement is correct?

    Question 19: JAVA OOPS - Final Class Example

    Which of the following will cause an error?

    final class A {}
class B extends A {}

    Question 20: JAVA OOPS - equals() Overriding

    Which statement is correct about equals() method?