Programming Questions and Exercises: Loops
Question 1
Write a
program to print numbers from 1 to 10.
Show the
answer.
public class PrintNumbers
{
public static void main(String[] args)
{
for(int i=1; i<=10; i++)
{
System.out.println(i);
}
}
}
Question 2
Write a
program to calculate the sum of first 10 natural number.
Show the
answer.
public class SumNumbers
{
public static void main(String[] args)
{
int sum = 0;
for(int i=1; i<=10; i++)
{
sum += i;
}
System.out.println("Sum: " + sum);
}
}
Question 3
Write a
program that prompts the user to input a positive integer. It should then print
the multiplication table of that number.
Show the
answer.
import java.util.Scanner;
public class Table
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int num;
System.out.print("Enter any positive integer: ");
num = console.nextInt();
System.out.println("Multiplication Table of " + num);
for(int i=1; i<=10; i++)
{
System.out.println(num +" x " + i + " = " + (num*i)
);
}
}
}
Question 4
Write a
program to find the factorial value of any number entered through the
keyboard.
Show the
answer.
import java.util.Scanner;
public class FactorialDemo1
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int num; // To hold number
int fact = 1; // To hold factorial
System.out.print("Enter any positive integer: ");
num = console.nextInt();
for(int i=1; i<=num; i++)
{
fact *= i;
}
System.out.println("Factorial: "+
fact);
}
}
Question 5
Two
numbers are entered through the keyboard. Write a program to find the value of
one number raised to the power of another. (Do not use Java built-in method)
Show the
answer.
import java.util.Scanner;
public class PowerDemo
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int base;
int power;
int result = 1;
System.out.print("Enter the base number ");
base = console.nextInt();
System.out.print("Enter the power ");
power = console.nextInt();
for(int i = 1; i <= power; i++)
{
result *= base;
}
System.out.println("Result: "+
result);
}
}
Question 6
Write a
program that prompts the user to input an integer and then outputs the number
with the digits reversed. For example, if the input is 12345, the output should
be 54321.
Show the
answer.
import java.util.Scanner;
public class ReverseNumber
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int number;
int reverse = 0;
System.out.print("Enter the number ");
number = console.nextInt();
int temp = number;
int remainder = 0;
while(temp>0)
{
remainder = temp %
10;
reverse = reverse
* 10 + remainder;
temp /= 10;
}
System.out.println("Reverse of "
+ number + " is " + reverse);
}
}
Question 7
Write a
program that reads a set of integers, and then prints the sum of the even and
odd integers.
Show the
answer.
import java.util.Scanner;
public class ReadSetIntegers
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int number;
char choice;
int evenSum = 0;
int oddSum = 0;
do
{
System.out.print("Enter the number ");
number = console.nextInt();
if( number % 2 == 0)
{
evenSum += number;
}
else
{
oddSum += number;
}
System.out.print("Do you want to continue y/n? ");
choice = console.next().charAt(0);
}while(choice=='y' || choice == 'Y');
System.out.println("Sum of even numbers: " + evenSum);
System.out.println("Sum of odd numbers: " + oddSum);
}
}
Question 8
Write a
program that prompts the user to input a positive integer. It should then
output a message indicating whether the number is a prime number.
Show the
answer.
import java.util.Scanner;
public class TestPrime
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int number;
System.out.print("Enter the positive integer ");
number = console.nextInt();
boolean flag = true;
for(int i = 2; i < number; i++)
{
if(number % i == 0)
{
flag = false;
break;
}
}
if(flag && number > 1)
{
System.out.println("Number is prime");
}
else
{
System.out.println("Number is not prime");
}
}
}
Question 9
Write a
program to calculate HCF of Two given number.
Show the
answer.
import java.util.Scanner;
public class FindHcf
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int dividend, divisor;
int remainder, hcf = 0;
System.out.print("Enter the first number ");
dividend = console.nextInt();
System.out.print("Enter the second number ");
divisor = console.nextInt();
do
{
remainder = dividend % divisor;
if(remainder == 0)
{
hcf = divisor;
}
else
{
dividend = divisor;
divisor = remainder;
}
}while(remainder != 0);
System.out.println("HCF: " + hcf);
}
}
Question 10
Write a
do-while loop that asks the user to enter two numbers. The numbers should be
added and the sum displayed. The loop should ask the user whether he or she
wishes to perform the operation again. If so, the loop should repeat; otherwise
it should terminate.
Show the
answer.
import java.util.Scanner;
public class SumAgain
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int number1, number2;
char choice;
do
{
System.out.print("Enter the first number ");
number1 = console.nextInt();
System.out.print("Enter the second number ");
number2 = console.nextInt();
int sum = number1 + number2;
System.out.println("Sum of numbers: "
+ sum);
System.out.print("Do you want to continue y/n? ");
choice = console.next().charAt(0);
System.out.println();
}while(choice=='y' || choice == 'Y');
}
}
Question 11
Write a
program to enter the numbers till the user wants and at the end it should
display the count of positive, negative and zeros entered.
Show the
answer.
import java.util.Scanner;
public class CountNumbers
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int number,
countPositive = 0,
countNegative = 0,
countZero = 0;
char choice;
do
{
System.out.print("Enter the number ");
number = console.nextInt();
if(number > 0)
{
countPositive++;
}
else if(number < 0)
{
countNegative++;
}
else
{
countZero++;
}
System.out.print("Do you want to continue y/n? ");
choice = console.next().charAt(0);
}while(choice=='y' || choice == 'Y');
System.out.println("Positive numbers: " + countPositive);
System.out.println("Negative numbers: " + countNegative);
System.out.println("Zero numbers: "
+ countZero);
}
}
Question 12
Write a
program to enter the numbers till the user wants and at the end the program
should display the largest and smallest numbers entered.
Show the
answer.
import java.util.Scanner;
public class FindMaxMin
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int number;
int max = Integer.MIN_VALUE; // Intialize max with minimum value
int min = Integer.MAX_VALUE; // Intialize min with maximum value
char choice;
do
{
System.out.print("Enter the number ");
number = console.nextInt();
if(number > max)
{
max = number;
}
if(number < min)
{
min = number;
}
System.out.print("Do you want to continue y/n? ");
choice = console.next().charAt(0);
}while(choice=='y' || choice == 'Y');
System.out.println("Largest number: "
+ max);
System.out.println("Smallest number: "
+ min);
}
}
Question 13
Write a program to print out all Armstrong numbers between 1 and
500. If sum of cubes of each digit of the number is equal to the number itself,
then the number is called an Armstrong number.
For example, 153 = ( 1 * 1 * 1 ) + ( 5 * 5 * 5 ) + ( 3 * 3 * 3 )
Show the
answer.
public class ArmstrongNumber
{
public static void main(String[] args)
{
int digit1, // To hold first digit (Ones) of number
digit2, //
To hold second digit (Tens) of number
digit3; //
To hold third digit (Hundreds) of number
for(int number = 1; number <= 500; number++)
{
int temp = number;
digit1 = temp % 10;
temp = temp / 10;
digit2 = temp % 10;
temp = temp / 10;
digit3 = temp % 10;
if(digit1*digit1*digit1 +
digit2*digit2*digit2 + digit3*digit3*digit3 == number)
{
System.out.println(number);
}
}
}
}
Question 14
Write a program to print Fibonacci series of n terms where n is
input by user :
0 1 1 2 3 5 8 13 24 .....
Show the
answer.
import java.util.Scanner;
public class FibonacciSeries
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int number; // To hold number of terms
int firstTerm = 0,
secondTerm = 1,
thirdTerm;
System.out.print("Enter number of terms of series : ");
number = console.nextInt();
System.out.print(firstTerm + " " +
secondTerm + " ");
for(int i = 3; i <= number; i++)
{
thirdTerm = firstTerm + secondTerm;
System.out.print(thirdTerm + " ");
firstTerm = secondTerm;
secondTerm = thirdTerm;
}
}
}
Question 15
Write a program to calculate the sum of following series where n
is input by user.
1 + 1/2 + 1/3 + 1/4 + 1/5 +…………1/n
Show the
answer.
import java.util.Scanner;
public class SumOfSeries
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int number; // To hold number of terms
double sum = 0;
System.out.print("Enter number of terms of series : ");
number = console.nextInt();
for(int i = 1; i <= number; i++)
{
sum += 1.0/i;
}
System.out.println("sum: " + sum);
}
}
Question 16
Compute the natural logarithm of 2, by adding up to n terms in the
series
1 - 1/2 + 1/3 - 1/4 + 1/5 -... 1/n
where n is a positive integer and input by user.
Show the
answer.
import java.util.Scanner;
public class Ln2
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int number; // To hold number of terms
System.out.print("Enter number of terms of series : ");
number = console.nextInt();
double sum = 0;
int sign = 1;
for(int i = 1; i <= number; i++)
{
sum += (1.0 * sign) / i;
sign *= -1;
}
System.out.println("log2: "
+ sum);
}
}
Question 17
Write a
program that generates a random number and asks the user to guess what the
number is. If the user's guess is higher than the random number, the program
should display "Too high, try again." If the user's guess is lower
than the random number, the program should display "Too low, try
again." The program should use a loop that repeats until the user
correctly guesses the random number.
Show the
answer.
import java.util.Scanner;
public class GuessMyNumber
{
public static void main(String[] args)
{
Scanner console = new Scanner(System.in);
int number, // To hold the random
number
guess, //
To hold the number guessed by user
tries = 0; // To hold number of tries
number = (int) (Math.random() * 100)
+ 1; // get random number between 1 and 100
System.out.println("Guess My Number Game");
System.out.println();
do
{
System.out.print("Enter a guess between 1 and 100 : ");
guess = console.nextInt();
tries++;
if (guess > number)
{
System.out.println("Too high! Try Again");
}
else if (guess < number)
{
System.out.println("Too low! Try Again");
}
else
{
System.out.println("Correct! You got
it in " + tries + " guesses!");
}
}while (guess != number);
}
}
