10 Basics Programs using for(), while() and do-while() (Java)

So today I am going to give you some of the programs using for() loop, while() loop and do-while() loop. If you know the basics of the for() loop, while() loop and do-while() loop or if you have followed our earlier blogs then you will be able to write the codes which I am going to give. The programs which I am going to give, first you try to do it by yourself and then you can match the solution which I have provided. So without any further delay lets get started.

Q1. Write a program to calculate and print the sum of first n natural numbers. The integer n is to be entered by the user.

Solution:

 import java.util.*;
 class Sum
 {
     public void main()
     {
         Scanner sc = new Scanner(System.in);
         System.out.println("Input a integer: ");
         int n = sc.nextInt();
         int sum = 0;
         for(int i = 1;i <= n;i++)
         {
             sum = sum+i;
         }
         System.out.println("Sum = " + sum);
     }
 }

Output:
Input a integer: 
5
Sum = 15

Q2. Write a program to calculate and print the sum of odd numbers and sum of even numbers for the first n natural numbers. The integer n is to be entered by the user.

Solution:

 import java.util.*;
 class Sum
 {
     public void main()
     {
         Scanner sc = new Scanner(System.in);
         System.out.println("Input a integer: ");
         int n = sc.nextInt();
         int sumEven = 0,sumOdd = 0;
         for(int i = 1;i <= n;i++)
         {
             if(i%2 == 0)
             {
                 sumEven = sumEven+i;
             }
             else
             {
                 sumOdd = sumOdd+i;
             }
         }
         System.out.println("Sum of Even Numbers = " + sumEven);
         System.out.println("Sum of Odd Numbers = " + sumOdd);
     }
 }

Output:
Input a integer: 
10
Sum of Even Numbers = 30
Sum of Odd Numbers = 25

Q3. Write a program to calculate factorial of a number using for() loop, which is calculated by multiplying all natural numbers starting from q to the given number or reverse of it i.e. from the given number to 1. 

For Example. Factorial of 4 => 1*2*3*4 = 24 or  4*3*2*1=24.

Solution:

 import java.util.*;
 class Factorial_For_Loop
 {
     public void main()
     {
         Scanner sc = new Scanner(System.in);
         System.out.println("Input a number: ");
         int n = sc.nextInt();
         int c = n;
         System.out.print(c);
         for(int i = n-1;i > 0;i--)
         {
             c = c*i;
             System.out.print("*" + i);
         }
         System.out.println("=" + c);
     }
 }

Output:
Enter a number: 
4
4*3*2*1=24

Q4. Write a program to calculate factorial of a number using do-while() loop, which is calculated by multiplying all natural numbers starting from q to the given number or reverse of it i.e. from the given number to 1. 

For Example. Factorial of 4 => 1*2*3*4 = 24 or  4*3*2*1=24.

Solution:

 import java.util.*;
 class Factorial_Do_While_Loop
 {
     public void main()
     {
         Scanner sc = new Scanner(System.in);
         System.out.println("Input a number: ");
         int n = sc.nextInt();
         int c = n;
         System.out.print(c);
         int i = n-1;
         do
         {
             c = c*i;
             System.out.print("*" + i);
             i--;
         }
         while(i > 0);
         System.out.print("=" + c);
     }
 }

Output:
Input a number: 
4
4*3*2*1=24

Q5. Write a program to input a number and check whether it is a prime number or not using for() loop.

[A number is said to be prime if the number has only two factors i.e. the number is divisible by one and itself and no other factor or a number is divisible by 1 and itself and not divisible by any other factor of it.]

For Example: 2,3,5,7...etc are prime numbers.

Solution:

 import java.util.*;
 class PrimeNumber_For_Loop
 {
     public void main()
     {
         Scanner sc = new Scanner(System.in);
         System.out.println("Input a number: ");
         int n = sc.nextInt();
         int count = 0;
         for(int i = 1;i <= n;i++)
         {
             if(n%i == 0)
             {
                 count++;
             }
         }
         if(count == 2)
         {
             System.out.println(n + " is a Prime Number");
         }
         else
         {
             System.out.println(n + " is not a Prime Number");
         }
     }
 }

Output:
Input a number: 
5
5 is a Prime Number

Q6. Write a program to input a number and check whether it is a prime number or not using while() loop.

[A number is said to be prime if the number has only two factors i.e. the number is divisible by one and itself and no other factor or a number is divisible by 1 and itself and not divisible by any other factor of it.]

For Example: 2,3,5,7...etc are prime numbers.

Solution:

 import java.util.*;
 class PrimeNumber_While_Loop
 {
     public void main()
     {
         Scanner sc = new Scanner(System.in);
         System.out.println("Input a number: ");
         int n = sc.nextInt();
         int i = 1,count = 0;
         while(i <= n)
         {
             if(n%i == 0)
             {
                 count++;
             }
             i++;
         }
         if(count == 2)
         {
             System.out.println(n + " is a Prime Number");
         }
         else
         {
             System.out.println(n + " is not a Prime Number");
         }
     }
 }

Output:
Input a number: 
7
7 is a Prime Number

Q7. Write a program to input an integer. Print whether the integer is an Armstrong number or not using for() loop.

[If the original number and sum of cubes of all its digit are same then the number is Armstring.]

For Example: 135 is an Armstrong Number, as 1*1*1+3*3*3+5*5*5=135.

Solution:

 import java.util.*;
 class ArmstrongNumber_For_Loop
 {
     public void main()
     {
         Scanner sc = new Scanner(System.in);
         System.out.println("Input a number: ");
         int n = sc.nextInt();
         int reminder,sum = 0;
         for(int i = n;i > 0;i = i/10)
         {
             reminder = i%10;
             sum = sum+reminder*reminder*reminder;
         }
         if(sum == n)
         {
             System.out.println(n + " is an Armstrong Number");
         }
         else
         {
             System.out.println(n + " is not an Armstrong Number");
         }
     }
 }

Output:
Input a number: 
153
153 is an Armstrong Number

Q8. Write a program to input an integer. Print whether the integer is an Armstrong number or not using while() loop.

[If the original number and sum of cubes of all its digit are same then the number is Armstring.]

For Example: 135 is an Armstrong Number, as 1*1*1+3*3*3+5*5*5=135.

Solution:

 import java.util.*;
 class ArmstrongNumber_While_Loop
 {
     public void main()
     {
         Scanner sc = new Scanner(System.in);
         System.out.println("Input a number: ");
         int n = sc.nextInt();
         int i = n,reminder,sum = 0;
         while(i > 0)
         {
             reminder = i%10;
             sum = sum+reminder*reminder*reminder;
             i = i/10;
         }
         if(sum == n)
         {
             System.out.println(n + " is an Armstrong Number");
         }
         else
         {
             System.out.println(n + " is not an Armstrong Number");
         }
     }
 }

Output:
Input a number: 
153
153 is an Armstrong Number

Q9. Write a program to input an integer. Print whether the integer is a Palindrome number or not using for() loop.

[If the original number and its reverse are same then number is Palindrome.]

For Example: 151 and its reverse is 151, So 151 is a Palindrome number.

Solution:

 import java.util.*;
 class PalindromeNumber_For_Loop
 {
     public void main()
     {
         Scanner sc = new Scanner(System.in);
         System.out.println("Input a number: ");
         int n = sc.nextInt();
         int reminder,sum = 0;
         for(int i = n;i > 0;i = i/10)
         {
             reminder = i%10;
             sum = sum*10+reminder;
         }
         if(n == sum)
         {
             System.out.println(n + " is a Palindrome Number");
         }
         else
         {
             System.out.println(n + " is not a Palindrome Number");
         }
     }
 }

Output:
Input a number: 
151
151 is a Palindrome Number

Q10. Write a program to input an integer. Print whether the integer is a Palindrome number or not using while() loop.

[If the original number and its reverse are same then number is Palindrome.]

For Example: 151 and its reverse is 151, So 151 is a Palindrome number.

Solution:

 import java.util.*;
 class PalindromeNumber_While_Loop
 {
     public void main()
     {
         Scanner sc = new Scanner(System.in);
         System.out.println("Input a number: ");
         int n = sc.nextInt();
         int i = n,reminder,sum = 0;
         while(i > 0)
         {
             reminder = i%10;
             sum = sum*10+reminder;
             i = i/10;
         }
         if(n == sum)
         {
             System.out.println(n + " is a Palindrome Number");
         }
         else
         {
             System.out.println(n + " is not a Palindrome Number");
         }
     }
 }

Output:
Input a number: 
151
151 is a Palindrome Number

So that is it for the for() loop, while() loop and do-while() loop programs. Hope you find it useful and if you have any query do comment in the comment box and I will try to solve your query.

Thank You.