2

2.6
import java.util.Scanner;
       public class test
{
       public static void main(String[] args)
   {
              int a;
              Scanner input=new Scanner(System.in);
              System.out.print("Enter a number between 0-1000:");
              int b=input.nextInt();
        if(b >= 0 && b <= 1000)
        {
              a= b%10 + b/10%10 + b/100%10 +b/1000;
              System.out.println("Sum of several numbers "+a);
        }
        else
        {
           System.out.println("Error!"); 
        }
   }
}

2.15


import java.util.Scanner;

public class test 
{
    public static void main(String[] args) 
    {
        Scanner input=new Scanner(System.in);
        double x1,x2,y1,y2;
        System.out.println("Enter the x1 ");
        x1 = Double.valueOf(input.nextInt());
        System.out.println("Enter the y1 ");
        y1 = Double.valueOf(input.nextInt());
        System.out.println("Enter the x2 ");
        x2 = Double.valueOf(input.nextInt());
        System.out.println("Enter the y2 ");
        y2 = Double.valueOf(input.nextInt());
        System.out.println("The distance between the two points is "+ Math.pow((Math.pow((x2 - x1),2)+Math.pow((y2 - y1),2)),0.5));

    }
}