Quiz - Programming With Java - Object Oriented Concepts

int[][] arr = new int[3][];

for (int i = 0; i < arr.length; i++)
    arr[i] = new int[3];

2. ► Code below has class VQClassB which inherits another class VQClassA, study following code carefully and choose correct option about output of program.

package com.vq.classes;

class VQClassA {
    public VQClassA(int x) {
        this.x = x;
    } protected int x;
}

public class VQClassB extends VQClassA {
    public VQClassB(int x, int x2, int y) {
        super(x);
        x = x2;
        this.y = y;
    } private VQClassB(int x, int y) {
        super(x);
        this.x = x;
        this.y = y;
    }

    private int x;

    private int y;

    public static void main(String[]args) {
        VQClassA vqa = new VQClassA(10);

        VQClassB vqb = new VQClassB(20, 10);

        vqa = vqb;
        System.out.println(vqa.x + " " + vqb.y);
    }
}

class VQCourse {
    public String courseName;
    public int courseID;
} public class VirtuQCourseProvide {

    public static void main(String[]args) {
        VQCourse course1 = new VQCourse();
         course1.courseID = 0001;
         course1.courseName = "0001";

        VQCourse course2 = new VQCourse();
         course2 = course1;

         System.out.println("course1.courseID = " + course1.courseID +
                            ", course2.courseID = " + course2.courseID);
}}

4. ► Java provided mechanism where classes can inherit commonly used state and behaviour of other classes.

package com.vq.inheritance;

public class VQJavaCourse extends VQCourse {
//Some implementation 
}

6. ► Which of following statement(s) can result in new object instance creation if executed successfully.

7. ► Following program have compilation error, can you guess root cause of it?

abstract class VQCourse {
    public String courseName;
    public String courseID;
} public class VirtuQCourseProvide extends VQCourse {

    public static void main(String[]args) {
        VQCourse course1 = new VQCourse();
         course1.courseID = "0001";
         course1.courseName = "JAVA";
         System.out.println(course1.toString());
}}

9. ► Code below has class VQClassB which inherits another class VQClassA, study following code carefully and choose correct option about program output.

package com.vq.classes;

public class VQClassB {
    class VQClassA {
        public VQClassA(int x) {
            this.x = x;
        } protected int x;
    } public VQClassB(int x, int x2, int y) {
        x = x2;
        this.y = y;
    }

    private VQClassB(int x, int y) {
        this.x = x;
        this.y = y;
    }

    private int x;

    private int y;

    public static void main(String[]args) {
        VQClassB vqb = new VQClassB(20, 10);

        VQClassB.VQClassA vqa = new VQClassB(10, 10).new VQClassA(10);

        System.out.println(vqa.x + " " + vqb.x);
    }
}

10. ► You only want to declare the behaviour of a certain type without any implemention , you should declare it as interface. In its most common form, an interface is a group of related methods with empty bodies.

package com.vq.inheritance;

public interface VQCourse {

    public void printCourseDetail();

    public void getCoursePrice();

}

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