How to check if a number is Harshad number in Java?

Harshad number is divisible by the sum of its digits. Simply put, if the sum of all the digits of a number is a factor of that number, then it is a Harshad number.

In this article, we will see how to check Harshad number using Java programming language.

Show you some examples

Example 1

Enter the number as 18

Let us check it using the logic of Harshad number −

The sum of the digits of the number = 1 8 = 9.

So, 18 is divisible by 9.

Therefore, 18 is a Harshad number.

Instance-2

Instance-2

The number entered is 3

Let us check it using the logic of Harshad number −

The sum of the digits of the number = 3.

So, 3 can be divided by 3.

Therefore, 3 is the Harshad number.

Instance-3

Instance-3

Enter the number as 15

Let us check it using the logic of Harshad number −

The sum of the digits of the number = 1 5 = 6.

So, 15 is not divisible by 6.

Therefore, 14 is not a Harshad number.

Some other examples of Harshad numbers include 1, 2, 4, 5, 6, 7, 8, 9, 10, 12, 18, 20, etc.

grammar

Convert an integer value to a string value using the built-in toString() method.

The following is the syntax to convert an integer value to a string value, then find its length and assign the length to an integer variable to get the total number of digits in the number -

String str = Integer.toString(input_number);

To get the length of an integer, we will use the built-in length() method of the Java String class Method returns the length of the String object.

int length = st.length();

To get the character at a specific position/index in a string, we use the charAt() method. Where charAt(i)-‘0’ returns the actual integer value.

int num = st.charAt(i)-‘0’;

Where "st" refers to the string, "i" is the iterator variable that iterates over the string.

algorithm

Algorithm 1

• Step 1 - Get an integer via initialization or user input.

• Step 2 - Find the sum of each digit of the number by iterating through each digit of the number.

• Step 3 - Then check if the original number is divisible by the sum of all digits of the number. The given number is a Harshad number if it is divisible, otherwise it is not a Harshad number

Algorithm 2

• Step 1 - Get an integer via initialization or user input.

• Step 2 - Convert the integer to a string using the built-in toString() method.

• Step 3 - Find the length of the string by using the built-in length() method.

• Step 4 - Then by using a for loop, iterate until the length of the string and get an integer value 0' from the string using charAt(i)-' And record the sum of all numbers.

• Step 5 - Then check if the original number is divisible by the sum of all digits of that number. The given number is a Harshad number if it is divisible, otherwise it is not a Harshad number.

Multiple methods

We provide solutions in different ways

• Do not use strings

• By using strings

Let’s look at the program and its output one by one.

Method 1: Not using strings

In this method, an integer value will be initialized in the program, and then by using Algorithm-1 we can check whether a number is a Harshad number.

Example

public class Main{
   //main method
   public static void main(String args[]){

      //Declared an integer variable and initialized a number as value
      int originalNumber = 21;

      //printing the given number to be checked
      System.out.println("Given number: "+originalNumber);

      //keep a copy of original number
      int copyOfOriginalNumber = originalNumber;

      //initialize sum as 0
      int sum = 0;

      //Find sum of all digits of the number
      //continue the loop till the number is greater than 0
      while(originalNumber > 0){

         //get the rightmost digit of the number by using % operator
         int rem = originalNumber%10;

         //add the digit(rem) to sum
         sum = sum + rem;

         //remove the rightmost digit from number and get the updated number
         originalNumber = originalNumber/10;
      }

      //printing the result
      if(copyOfOriginalNumber % sum == 0)
         System.out.println(copyOfOriginalNumber+" is a Harshadnumber");
      else
         System.out.println(copyOfOriginalNumber+" is not a Harshadnumber");
   }
}

Output

Given number: 21
21 is a Harshad number

Method 2: Using strings

In this method, an integer value will be initialized in the program and then using Algorithm-2 we will check whether the number is a Harshad number or not.

Example

public class Main{
   //main method
   public static void main(String args[]){

      //Declared an integer variable and initialized a number as value
      int originalNumber = 40;

      //printing the given number to be checked
      System.out.println("Given number: "+originalNumber);

      //keep a copy of original number
      int copyOfOriginalNumber = originalNumber;

      //initialize sum as 0
      int sum = 0;

      //convert the integer to string by using toString() method
      String str = Integer.toString(originalNumber);
       
      //find length of String by using length() method
      //which is nothing but total number of digits in the given number
      int length=str.length();
       
      //iterate the String and get the digits by using charAt(i)-'0'
      //find the sum of digits
      for(int i = 0; i < length; i++){
         sum += str.charAt(i)-'0';
      }

      //printing the result 
      if(copyOfOriginalNumber % sum == 0)
         System.out.println(copyOfOriginalNumber+" is a Harshad number");
      else
         System.out.println(copyOfOriginalNumber+" is not a Harshad number");      
   }
}

Output

Given number: 40
40 is a Harshad number

In this article, we explored how to check if a number is a Harshad number in Java using different methods.

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