1. Sum of N numbers

 1. SUM OF N NUMBERS    

  //sum of n numbers

  import java.util.*;
  import java.util.Scanner;

  public class Sum
  {
      public static void main(String[] args)
      {
          Scanner sc = new Scanner(System.in);
          int n = sc.nextInt();
          int sum=0;
          for(int i=0;i < = n;i++)
          {
              sum=sum+i;
          }
          System.out.println(sum);
      }
  }

2. Sum of Digits.

  //Sum of Digits

  import java.util.*;
  import java.util.Scanner;

  public class Sum
  {
     public static void main(String[] args)
      {
          Scanner sc = new Scanner(System.in);
          int a = sc.nextInt();
          int rem,result=0,i;
          for(i=a;a!=0;a/=10)
          {
              rem = a%10;
              result+=rem;

          }
          System.out.println("The sum of digits: "+i+" is "+result);
      } 
  }