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Java Method Exercises: Compute the sum of the digits in an integer

Java Method: Exercise-6 with Solution

Write a Java method to compute the sum of the digits in an integer.

Test Data:
Input an integer: 25

Pictorial Presentation:

Java Method Exercises: Compute the sum of the digits in an integer

Sample Solution:

Java Code:

import java.util.Scanner;
public class Exercise6 {

  public static void main(String[] args)
    {
      Scanner in = new Scanner(System.in);
      System.out.print("Input an integer: ");
      int digits = in.nextInt();
	  System.out.println("The sum is " + sumDigits(digits));
    }

 public static int sumDigits(long n) {
		int result = 0;
		
		while(n > 0) {
			result += n % 10;
			n /= 10;
		}
		
		return result;
	}
	
 }

Sample Output:

Input an integer: 25                                                                                          
The sum is 7

Flowchart:

Flowchart: Compute the sum of the digits in an integer

Java Code Editor:

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Next: Write a Java method to display the first 50 pentagonal numbers.

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Java: Tips of the Day

Array vs ArrayLists:

The main difference between these two is that an Array is of fixed size so once you have created an Array you cannot change it but the ArrayList is not of fixed size. You can create instances of ArrayLists without specifying its size. So if you create such instances of an ArrayList without specifying its size Java will create an instance of an ArrayList of default size.

Once an ArrayList is full it re-sizes itself. In fact, an ArrayList is internally supported by an array. So when an ArrayList is resized it will slow down its performance a bit as the contents of the old Array must be copied to a new Array.

At the same time, it's compulsory to specify the size of an Array directly or indirectly while creating it. And also Arrays can store both primitives and objects while ArrayLists only can store objects.

Ref: https://bit.ly/3o8L2KH