Q: Question 3How are these statements different from each other:(i) break(ii) continue(iii) System.exit(0)

(i) The break statement terminates the current loop or switch statement. The execution then continues from the statement immediately following the current loop or switch statement.(ii) The continue statement tells the computer to skip the rest of the current iteration of the loop. However, instead of jumping out of the loop completely like break statement, it jumps back to the beginning of the loop and continues with the next iteration. This includes the evaluation of the loop controlling condition to check whether any further iterations are required.(iii) Unlike break and continue statements which are used to control the flow of execution, System.exit(0) command terminates the execution of the program by stopping the Java Virtual Machine which is executing the program. It is generally used when due to some reason it is not possible to continue with the execution of the program.

Q: Question 7What are the differences between while loop and do-while loop?

do-while loopwhile loopdo-while is an exit-controlled loop.while is an entry-controlled loop.do-while loop checks the test condition at the end of the loop.while loop checks the test condition at the beginning of the loop.do-while loop executes at least once, even if the test condition is false.while loop executes only if the test condition is true.do-while loop is suitable when we need to display a menu to the user.while loop is helpful in situations where number of iterations is not known.

Q: Question 8(i)How many times are the following loop bodies repeated? What is the final output in each case?int x = 1; while (x < 10) if(x % 2 == 0) System.out.println(x);

The loop repeats for infinite times.OutputThe given code gives no output.ExplanationThe value of x is 1. The test condition of while loop — x < 10 is true but the test condition of if — x % 2 == 0 is false. In the absence of update expression, the while loop continues infinitely.

Q: Question 8(ii)How many times are the following loop bodies repeated? What is the final output in each case?int y = 1; while (y < 10) if (y % 2 == 0) System.out.println(y++);

The loop repeats for infinite times.OutputThe given code gives no output.ExplanationThe value of y is 1. The test condition of while loop — y < 10 is true but the test condition of if — y % 2 == 0 is false. Thus, the control does not enter the if statement and the value of y remains 1 infinitely. Thus, the while loop continues infinitely.

Q: Question 8(iii)How many times are the following loop bodies repeated? What is the final output in each case?int z = 1; while (z < 10) if((z++) % 2 == 0) System.out.println(z);

The loop executes 9 times.Output3 5 7 9 ExplanationThe loop executes 9 times. Value of z is printed 4 times inside the loop. The condition if((z++) % 2 == 0) will be false when z is odd and true when z is even. Value of z will be incremented after if check is performed due to post increment operator z++. Execution of the loop is summarized in the table below:Iterationsz(z++) % 2 == 0OutputRemarks1st1False Value of z becomes 2 after if check as z++ increments it after the evaluation of (z++) % 2 == 02nd2True3z becomes 3 after if check, hence 3 is printed in this iteration.3rd3False z becomes 4.4th4True5z becomes 5.5th5False z becomes 6.6th6True7z becomes 7.7th7False z becomes 8.8th8True9z becomes 9.9th9False z becomes 10.As value of z is now 10, the test condition of while loop becomes false hence, 10th iteration of the loop is not executed.

Q: Question 9Write a program to accept n number of input integers and find out:i. Number of positive numbersii. Number of negative numbersiii. Sum of positive numbers

import java.util.Scanner; public class KboatIntegers { public static void main(String args[]) { Scanner in = new Scanner(System.in); int pSum = 0, pCount = 0, nCount = 0; System.out.print("Enter the number of integers: "); int num = in.nextInt(); System.out.println("Enter " + num + " integers: "); for (int i = 1; i <= num; i++) { int n = in.nextInt(); if (n >= 0) { pSum += n; pCount++; } else nCount++; } System.out.println("Positive numbers = " + pCount); System.out.println("Negative numbers = " + nCount); System.out.println("Sum of positive numbers = " + pSum); } }Output

Question 1

Question 1What are looping control structures?

Accepted Answer

A loop is a set of instructions that is continually repeated until a certain condition is met. Looping control structures refer to certain looping constructs which execute a block of code repeatedly until a certain condition remains true. For example, for loop, while loop, do - while loop etc.

Question 2

Question 2What are the essential parts of a looping control structure?

Accepted Answer

The essential parts of a looping control structure are as follows:Initialisation — This segment initialises the loop control variable before starting the loop. It is executed only once at the beginning of the loop.For example, int counter = 1;Test-condition — The test-condition is the expression that is evaluated at the beginning of each iteration. Its value determines whether the body of the loop is to be executed (test condition is true) or the loop is to be terminated (test condition is false).For example, counter <= 10Update — This is the increment or decrement operation of the control variable. This operation is performed at the end of each iteration.For example, counter++ ;

Question 3

Question 3How are these statements different from each other:(i) break(ii) continue(iii) System.exit(0)

Accepted Answer

(i) The break statement terminates the current loop or switch statement. The execution then continues from the statement immediately following the current loop or switch statement.(ii) The continue statement tells the computer to skip the rest of the current iteration of the loop. However, instead of jumping out of the loop completely like break statement, it jumps back to the beginning of the loop and continues with the next iteration. This includes the evaluation of the loop controlling condition to check whether any further iterations are required.(iii) Unlike break and continue statements which are used to control the flow of execution, System.exit(0) command terminates the execution of the program by stopping the Java Virtual Machine which is executing the program. It is generally used when due to some reason it is not possible to continue with the execution of the program.

Question 4

Question 4(i)Identify all the errors in the following repetitive statements.for	(int i = 5; i > 0; i++)
{
    System.out.println("Java");
}

Accepted Answer

The test expression i > 0 will always remain true and hence, the for loop will become an infinite loop and keep on iterating.

Question 5

Question 5What is an empty statement? Explain its usefulness.

Accepted Answer

Empty statement consists only of a semicolon ;. It is useful when we want to make a loop an empty loop.To make a for loop an empty loop, we write the following code:for (int i = 1 ; i <=10 ; i ++);

Question 6

Question 7What are the differences between while loop and do-while loop?

Accepted Answer

do-while loopwhile loopdo-while is an exit-controlled loop.while is an entry-controlled loop.do-while loop checks the test condition at the end of the loop.while loop checks the test condition at the beginning of the loop.do-while loop executes at least once, even if the test condition is false.while loop executes only if the test condition is true.do-while loop is suitable when we need to display a menu to the user.while loop is helpful in situations where number of iterations is not known.

Question 7

Question 8(i)How many times are the following loop bodies repeated? What is the final output in each case?int x = 1;
while (x < 10)
    if(x % 2 == 0)
        System.out.println(x);

Accepted Answer

The loop repeats for infinite times.OutputThe given code gives no output.ExplanationThe value of x is 1. The test condition of while loop — x < 10 is true but the test condition of if — x % 2 == 0 is false. In the absence of update expression, the while loop continues infinitely.

Question 8

Question 8(ii)How many times are the following loop bodies repeated? What is the final output in each case?int y = 1;
while (y < 10)
    if (y % 2 == 0)
        System.out.println(y++);

Accepted Answer

The loop repeats for infinite times.OutputThe given code gives no output.ExplanationThe value of y is 1. The test condition of while loop — y < 10 is true but the test condition of if — y % 2 == 0 is false. Thus, the control does not enter the if statement and the value of y remains 1 infinitely. Thus, the while loop continues infinitely.

Question 9

Question 8(iii)How many times are the following loop bodies repeated? What is the final output in each case?int	z = 1;
while (z < 10)
    if((z++) % 2 == 0)
        System.out.println(z);

Accepted Answer

The loop executes 9 times.Output3   
5   
7   
9   
ExplanationThe loop executes 9 times. Value of z is printed 4 times inside the loop. The condition if((z++) % 2 == 0) will be false when z is odd and true when z is even. Value of z will be incremented after if check is performed due to post increment operator z++. Execution of the loop is summarized in the table below:Iterationsz(z++) % 2 == 0OutputRemarks1st1False Value of z becomes 2 after if check as z++ increments it after the evaluation of (z++) % 2 == 02nd2True3z becomes 3 after if check, hence 3 is printed in this iteration.3rd3False z becomes 4.4th4True5z becomes 5.5th5False z becomes 6.6th6True7z becomes 7.7th7False z becomes 8.8th8True9z becomes 9.9th9False z becomes 10.As value of z is now 10, the test condition of while loop becomes false hence, 10th iteration of the loop is not executed.

Question 10

Question 9Write a program to accept n number of input integers and find out:i. Number of positive numbersii. Number of negative numbersiii. Sum of positive numbers

Accepted Answer

import java.util.Scanner;

public class KboatIntegers
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        int pSum = 0, pCount = 0, nCount = 0;
        System.out.print("Enter the number of integers: ");
        int num = in.nextInt();
        
        System.out.println("Enter " + num + " integers: ");
        for (int i = 1; i <= num; i++) {
            int n = in.nextInt();
            if (n >= 0) {
                pSum += n;
                pCount++;
            }
            else 
                nCount++;
        }
        
        System.out.println("Positive numbers = " + pCount);
        System.out.println("Negative numbers = " + nCount);
        System.out.println("Sum of positive numbers  = " + pSum);
    }
}Output

Question 11

Question 10Write a program using do-while loop to compute the sum of the first 50 positive odd integers.

Accepted Answer

public class KboatSumOdd
{
    public static void main(String args[]) {
        long sumOdd = 0;
        int i = 1;
        do {
            sumOdd += i;
            i += 2;
        } while(i <= 50);
                    
        System.out.println("Sum of 50 odd positive numbers = " + sumOdd);        
    }
}Output

Question 12

Question 11Write a program to read the number n via the Scanner class and print the Tribonacci series:0, 0, 1, 1, 2, 4, 7, 13, 24, 44, 81 ...and so on.Hint: The Tribonacci series is a generalisation of the Fibonacci sequence where each term is the sum of the three preceding terms.

Accepted Answer

import java.util.Scanner;

public class KboatTribonacci
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter no. of terms : ");
        int n = in.nextInt();
        
        if(n < 3)
            System.out.print("Enter a number greater than 2");
        else    {
            int a = 0, b = 0, c = 1;
            System.out.print(a + " " + b + " " + c);
        
            for (int i = 4; i <= n; i++) {
                int term = a + b + c;
                System.out.print(" " + term);
                a = b;
                b = c;
                c = term;
            }
        }
    }
}Output

Question 13

Question 12Write a program to calculate the value of Pi with the help of the following series:Pi = (4/1) - (4/3) + (4/5) - (4/7) + (4/9) - (4/11) + (4/13) - (4/15) ...Hint: Use while loop with 100000 iterations.

Accepted Answer

public class KboatValOfPi
{
        public static void main(String args[]) {
            double pi = 0.0d, j = 1.0d;
            int i = 1;
            while(i <= 100000)  {
                if(i % 2 == 0)
                    pi -= 4/j;
                else
                    pi += 4/j;
                j += 2;
                i++;
            }
            System.out.println("Pi = " + pi);
        
    }
}Output

Question 14

Question 13Write a menu-driven program to display the pattern as per user's choice:Pattern 1       Pattern 2ABCDE          BABCD            LLABC              UUUAB                EEEEAFor an incorrect option, an appropriate error message should be displayed.

Accepted Answer

import java.util.Scanner;

public class KboatMenuPattern
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter 1 for pattern 1");
        System.out.println("Enter 2 for Pattern 2");
        System.out.print("Enter your choice: ");
        int choice = in.nextInt();
        switch (choice) {
            case 1:
            for (int i = 69; i >= 65; i--) {
                for (int j = 65; j <= i; j++) {
                    System.out.print((char)j);
                }
                System.out.println();
            }
            break;

case 2:
            String word = "BLUE";
            int len = word.length();
            for(int i = 0; i < len; i++) {
                for(int j = 0; j <= i; j++) {
                    System.out.print(word.charAt(i));
                }
                System.out.println();
            }
            break;

default:
            System.out.println("Incorrect choice");
            break;

}
    }
}Output

Question 15

Question 14Write a program to input a number and check and print whether it is a Pronic number or not. (Pronic number is a number which is the product of two consecutive integers.)Example: 12 = 3 x 4                20 = 4 x 5                42 = 6 x 7

Accepted Answer

import java.util.Scanner;

public class KboatPronicNumber
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter the number to check: ");
        int num = in.nextInt();
        
        boolean isPronic = false;
        
        for (int i = 1; i <= num - 1; i++) {
            if (i * (i + 1) == num) {
                isPronic = true;
                break;
            }
        }
        
        if (isPronic)
            System.out.println(num + " is a pronic number");
        else
            System.out.println(num + " is not a pronic number");
    }
}Output

Question 16

Question 15Write a program to accept a number and check and display whether it is a spy number or not. (A number is spy if the sum of its digits equals the product of the digits.)Example: Consider the number, 1124. Sum of the digits = 1 + 1 + 2 + 4 = 8.Product of the digits = 1 * 1 * 2 * 4 = 8.

Accepted Answer

import java.util.Scanner;

public class KboatSpyNumber
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter Number: ");
        int num = in.nextInt();
        
        int digit, sum = 0;
        int orgNum = num;
        int prod = 1;
        
        while (num > 0) {
            digit = num % 10;
            
            sum += digit;
            prod *= digit;
            num /= 10;
        }
        
        if (sum == prod)
            System.out.println(orgNum + " is Spy Number");
        else
            System.out.println(orgNum + " is not Spy Number");
        
    }
}Output

Question 17

Question 16Write a program to accept a number and check and display whether it is a Niven number or not. (Niven number is a number which is divisible by the sum of its digits).Example:Consider the number 126.Sum of its digits is 1 + 2 + 6 = 9 and 126 is divisible by 9.

Accepted Answer

import java.util.Scanner;

public class KboatNivenNumber
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter number: ");
        int num = in.nextInt();
        int orgNum = num;
        
        int digitSum = 0;
        
        while (num != 0) {
            int digit = num % 10;
            num /= 10;
            digitSum += digit;
        }
        
        /*
         * digitSum != 0 check prevents
         * division by zero error for the
         * case when users gives the number
         * 0 as input
         */
        if (digitSum != 0 && orgNum % digitSum == 0)
            System.out.println(orgNum + " is a Niven number");
        else
            System.out.println(orgNum + " is not a Niven number");
    }
}Output

Question 18

Question 17Using the switch statement, write a menu driven program to:i. Generate and display the first 10 terms of the Fibonacci series 0, 1, 1, 2, 3, 5...The first two Fibonacci numbers are 0 and 1, and each subsequent number is the sum of the previous two.ii. Find the sum of the digits of an integer that is input.Sample Input: 15390Sample Output: Sum of the digits = 18For an incorrect choice, an appropriate error message should be displayed.

Accepted Answer

import java.util.Scanner;

public class KboatFibonacciNDigitSum
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("1. Fibonacci Series");
        System.out.println("2. Sum of digits");
        System.out.print("Enter your choice: ");
        int ch = in.nextInt();

switch (ch) {
            case 1:
            int a = 0, b = 1;
            System.out.print(a + " " + b);
            /*
             * i is starting from 3 below
             * instead of 1 because we have 
             * already printed 2 terms of
             * the series. The for loop will 
             * print the series from third
             * term onwards.
             */
            for (int i = 3; i <= 10; i++) {
                int term = a + b;
                System.out.print(" " + term);
                a = b;
                b = term;
            }
            break;

case 2:
            System.out.print("Enter number: ");
            int num = in.nextInt();
            int sum = 0;
            while (num != 0) {
                sum += num % 10;
                num /= 10;
            }
            System.out.println("Sum of Digits " + " = " + sum);
            break;

default:
            System.out.println("Incorrect choice");
            break;
        }
    }
}Output

Question 19

Question 18Write a program to input a number and print whether the number is a special number or not. (A number is said to be a special number, if the sum of the factorial of the digits of the number is same as the original number).

Accepted Answer

import java.util.Scanner;

public class KboatSpecialNum
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter number: ");
        int num = in.nextInt();

int t = num;
        int sum = 0, fact;
        while (t != 0) {
            int d = t % 10;
            fact = 1;
            for (int i = 1; i <= d; i++) 
                fact *= i;
            sum += fact;
            t /= 10;
        }

if (sum == num)
            System.out.println(num + " is a special number");
        else
            System.out.println(num + " is not a special number");

}
}Output

Question 20

Question 19Write a menu driven program to accept a number and check and display whether it is a Prime number or not OR an Automorphic Number or not. (Use switch-case statement).Prime number: A number is said to be a prime number if it is divisible only by 1 and itself and not by any other number.Example: 3, 5, 7, 11, 13 etc.Automorphic number: An automorphic number is the number which is contained in the last digit(s) of its square.Example: 25 is an automorphic number as its square is 625 and 25 is present as the last two digits.

Accepted Answer

import java.util.Scanner;

public class KboatPrimeAutomorphic
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("1. Prime number");
        System.out.println("2. Automorphic number");
        System.out.print("Enter your choice: ");
        int choice = in.nextInt();
        System.out.print("Enter number: ");
        int num = in.nextInt();

switch (choice) {
            case 1:
            int c = 0;
            for (int i = 1; i <= num; i++) {
                if (num % i == 0) {
                    c++;
                }
            }
            if (c == 2) 
                System.out.println(num + " is Prime");
            else
                System.out.println(num + " is not Prime");
            break;

case 2:
            int numCopy = num;
            int sq = num * num;
            int d = 0;

/*
             * Count the number of 
             * digits in num
             */
            while(num > 0) {
                d++;
                num /= 10;
            }

/*
             * Extract the last d digits
             * from square of num
             */
            int ld = (int)(sq % Math.pow(10, d));

if (ld == numCopy)
                System.out.println(numCopy + " is automorphic");
            else
                System.out.println(numCopy + " is not automorphic");
            break;

default:
            System.out.println("Incorrect Choice");
            break;
        }
    }
}Output

Iterative Constructs in Java

Assignment Questions

Multiple Choice Questions