Competency focused Practice Questions ISC Class XII Computer Science

class Vehicle
{
    protected String colour;
    protected String registration;

    public Vehicle(String c, String r)
    {
        colour = c;
        registration = r;
    }

    public void show()
    {
        System.out.println("Colour: " + colour);
        System.out.println("Registration number: " + registration);
    }
}

class Car extends Vehicle
{
    private double weight;
    private String model;

    public Car(String model, double weight,
               String colour, String registration)
    {
        this.model = model;
        this.weight = weight;

        super(colour, registration);
    }

    public void show()
    {
        super.show();

        System.out.println("Car Model name = " + model);
        System.out.println("Car body weight = " + weight);
    }
}

  

[Computational Complexity and Big-O Notation]

Question:

Finding the greatest common divisor (GCD) of two positive integers results in the time complexity of O(log N), where N is the larger number of two inputs. Justify the statement.

Question:

A student had written the following method to display “Hello World” four times:

void displayMessage()
{
    System.out.println("Hello World");
    System.out.println("Hello World");
    System.out.println("Hello World");
    System.out.println("Hello World");
}

Later, the student modified the code using a loop:

void displayMessage()
{
    int i = 1;
    while(i <= 4)
    {
        System.out.println("Hello World");
        i++;
    }
}

Compare the above code snippets with respect to time complexity.

Question:

Finding the greatest common divisor (GCD) of two positive integers results in the time complexity of O(log N), where N is the larger number of two inputs. Justify the statement.

double m = 1, n = 1;

for(int i = 0; i < x; i++)
{
    m *= Math.random();
}

for(int j = 0; j < y; j++)
{
    n *= Math.random();
}
    

[String and Arrays]

Question:

Find the output of the following snippet:

void check1()
{
    String x[] = {"Kolkata","Chennai","Delhi"};
    String y[] = {"Kolkata","Chennai","Delhi"};

    System.out.println(x.equals(y));
}

Answer:

false

[String]

Question:

Write the Java statement to print the position of the 2nd occurrence of the letter 'I' within the word "MICHIGAN".

[String]

Question:

Find the output:

System.out.println(
    "RocKet".substring(0, 4)
    .compareTo("Rock".replace('m', 'o'))
);

[Arrays]

Question:

What is the length of the array int arr[], if its first index is x and the last index is y?

[String]

Question:

How many String objects are created in the following snippet? Justify your answer.

String s1 = "Gujarat";

String s2 = new String("Gujarat");

String s3 = new String("Gujarat");

String s4 = "Gujarat";

[String]

Question:

Find the output of the following snippet:

String S1 = "AB", S2 = "BC";

for(int i = 0, j = 0; i < S1.length(); i++, j++)
{
    System.out.println(S1.charAt(i) + S2.charAt(j));
}

[Packages]

Question:

Why is the lang package termed as the default package in Java?

[Packages]

Question:

State the purpose of the following keywords in Java:

(a) package
(b) import

[Packages]

Question:

Given the following code snippet:

package mine;

public class Greetings
{
    public static void greet(String name)
    {
        System.out.println("Hello " + name + 
        ", welcome to the world of programming");
    }
}

import java.util.*;
import mine.*;

public class Trial
{
    public static void main()
    {
        Scanner sc = new Scanner(System.in);

        System.out.println("Give your name");

        String n = sc.next();

        Greetings.greet(n);
    }
}

(a) Predict the output for n = "Abhay".

(b) Explain the difference between:

import java.util.*;

and

import mine.*;

[Computer Hardware]

Question:

A 2 to 4 decoder contains 2 inputs denoted by A1 and A0 and 4 outputs denoted by D0, D1, D2, D3. Write the minterm representations for D1 and D3.

[Computer Hardware]

Question:

Write the canonical Product-of-Sum (POS) expression for the Sum and Carry of a Full Adder.

[Computer Hardware]

Question:

Following is the circuit diagram of a Full Adder. Redraw the circuit diagram by adding the missing logic gates.

---

[Computer Hardware]

Question:

Draw the logic circuit diagram for the simplified form of the following expression:

AB'C + AB'C + ABC

The circuit diagram should only contain:

• One AND gate
• One OR gate
• One NOT gate

Question Diagram:

Expression:

AB'C + AB'C + ABC

Answer:

Step 1: Simplification

AB'C + AB'C + ABC

= AB'C + ABC

= A(B'C + BC)

= AC

Simplified Expression:

AC

[Recursion]

Question:

Following method is a part of a class MyArray.

int check(int m[ ], int i)
{
    if(i <= 0)
    {
        return 0;
    }

    return check(m, i-2) + m[i-1];
}

public static void main()
{
    int m[ ] = {1, 2, 3, 4};

    int ans = check(m, m.length);

    System.out.println(ans);
}

(a) Predict the output of the code considering there is no compilation error. Show the working.

(b) Considering the if condition is changed to if(i < 0), how will it affect the output?

[Recursion]

Question:

A student has written the following code. It is written to check whether a string is palindrome or not. However, the code is not giving the desired result when the parameter “MADAM” is passed to the method isPalindrome(). Analyse the code and find out the logical error.

public class PalindromeTesting
{
    public static boolean isPalindrome(String word)
    {
        if(word.length() < 1)
        {
            return true;
        }

        else if(word.charAt(0) != word.charAt(word.length() - 1))
        {
            return false;
        }

        else
        {
            return isPalindrome(word.substring(0, word.length() - 1));
        }
    }
}

[Operation on File]

Question:

What is the difference between the following two statements?

1. FileWriter fw = new FileWriter();

2. FileWriter fw = new FileWriter(, true);

[String Tokenizer]

Question:

What is the difference between the two methods, nextToken() and hasMoreTokens() of StringTokenizer class?

int i;
for(i = 5; i >= 1; i--) {
    System.out.println();
}
System.out.println(i);

interface A
{
    final static int x = 5;

    abstract void abc();
}

interface B
{
    final static int y = 5;

    abstract void abc();
}