Lab Assignment #3 Exercise on While Loop:

Lab Assignment #3
Exercise on While Loop:
Objective-1 Use of While loop and operators
Problem Statement: Write a Java program that reads a positive integer and count the
number of digits.
Source Code:
class ArmstrongExample{
public static void main(String[] args) {
 int c=0,a,temp;
 int n=153;//It is the number to check armstrong
 temp=n;
 while(n>0)
 {
 a=n%10;
 n=n/10;
 c=c+1
 }
 System .out. println (“Number of digits in given number is”+c); }
}
Output:
Explanation: In every iteration, when we take the remainder, it will give the least significant bit
and store it in a variable. Then we divide the value by 10 to remove the least significant bit, since
int will only store the integer part.
Syntax:
while(Boolean expression)
{
Statement1;
Statement2;
…..
}
Objective-2 Use of while loop
Problem Statement: Write Java program to check if a number is Armstrong number or not
using while loop.
Note:371 is an Armstrong number because 3*3*3+7*7*7+1*1*1=371
Objective-3 Use of While loop
Problem Statement: Write a Java Program to print Fibonacci series up to a number n using
While loop.
Note:fab(0)=0,fab(1)=1,fib(2)=1,fib(3)=2,fib(4)=3……..
 fib(n)=fib(n-1)+fib(n-2) other than fib(0) and fib(1)
Exercise on do-while Loop
Objective-4: Use of Do While Loop
Problem Statement: Write a Java Program to calculate factorial of numbers between 10 to 15
using do-while and while loop.
Note:Factorial (5)=5*4*3*2*1
Source Code:
classTest{
publicstaticvoidmain(String args[]){
intnumber=10;
do
{
inti=1,fact=1;
//It is the number to calculate factorial
while(i<=number){
fact=fact*i;
i=i+1;
 }
System.out.println("Factorial of "+number+" is: "+fact);
number=number+1;
}while(number<=15); }
}
Output:
Explanation: factorial (n) = n*n-1*n-2*……..*1
Syntax:
do{
Statement1;
Statement2;
…..
} while(Boolean expression)
Objective-5: Use of do while loop.
Problem Statement: Write a java program to check whether number is strong number or not
using do- while loop.
Note:Strong number is a special number whose sum of factorial of digits is equal to the original number.
 145=!1+!4+!5
!5=5*4*3*2*1=120
!4=4*3*2*1=24
!1=1
So 145 is a Strong Number.
Objective-6: Use of do while loop.
Problem Statement: Write a Java program to find all prime factors of a number using do-while
loop.
Note: 45=1*3*3*5
So prime factors of 45 is 1,3,5
Exercise on For Loop
Objective-7: Use of for loop.
Problem Statement: Write a program in Java to display 20 terms of natural numbers and their
sum.
Problem Statement: Program that takes input as n natural numbers and print their sum on
output Screen.
Source Code:
public class Exercise11 {
 public static void main(String[] args) {
inti, sum=0; {
System.out.println("The first n natural numbers are :);
for(i=1;i<=20;i++) {
System.out.println(i);
 sum+=i;}
System.out.println("The Sum of 20 Natural Number are" +sum);
}}
Output
Explanation:Here we have used a simple for loop demo to print sum of natural numbers in its
each iteration.For that inside for loop, the value of i in each iteration itself is the natural number
starting from 1 to range(20), and we keep on adding into sum variable to get the final sum up-to
20 terms.
Syntax
for(initialization; boolean expression; update)
{
Statement1;
Statement2;
…..
}
Objective-8: Use of For Loop
Problem Statement: Write a program in Java to display the 20 terms of odd natural number and
their sum.
Note: For example 5 terms of odd natural numbers are-1,3,5,7,9
Objective-9: Use of for loop
Problem Statement:Generate all the prime numbers between 1 and 1000 using for loop.
Note: A prime number is an integer greater than 1 that is evenly divisible by only 1 and itself.
For example, 2, 3, 5, and 7 are prime numbers, but 4, 6, 8, and 9 are not.
Objective-10: Use of for loop
Problem Statement: Write a program in Java to display the pattern like right angle triangle with
a number.
1
12
123
1234
12345
123456
1234567
12345678
123456789
12345678910
Objective-11: Use of for loop
Problem Statement: Write a Java program to display the number rhombus structure.
The expected output is
 1
 212
 32123
 4321234
 543212345
65432123456
7654321234567
65432123456
 543212345
 4321234
 32123
 212
 1
Miscellaneous:
1. An interesting problem in number theory is sometimes called the “necklace problem.” This
problem begins with two single-digit numbers. The next number is obtained by adding the
first two numbers together and saving only the ones digit. This process is repeated until the
“necklace” closes by returning to the original two numbers. For example, if the starting two
numbers are 1 and 8, twelve steps are required to close the necklace: 1 8 9 7 6 3 9 2 1 3 4 7
1 8
Create a Necklace application that prompts the user for two single-digit integers and then
displays the sequence and the number of steps taken. The application output should look
similar to:
Enter the first starting number: 1
Enter the second starting number: 8 1 8 9 7 6 3 9 2 1 3 4 7 1 8
2. Let d(n) be defined as the sum of proper divisors of n (numbers less than n which divide
evenly into n).
If d(x) = y and d(y) = x, where x ≠ y, then x and y are an amicable pair and each of a and b are
called amicable numbers.
For example, the proper divisors of 220 are 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110;
therefore d(220) = 284. The proper divisors of 284 are 1, 2, 4, 71 and 142; so d(284) = 220.
Evaluate all pair of the amicable numbers less than 1000.