sum of numbers in java

public class Exercise2 {
public static void main(String[] args) {      
int my_array[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
int sum = 0;

for (int i : my_array)
    sum += i;
System.out.println("The sum is " + sum);
}
}

import java.io.*;
public class sd
{
  public static void main(String [] args)throws IOException
  {
     InputStreamReader hi = new InputStreamReader(System.in);
        BufferedReader in = new BufferedReader(hi);
        System.out.println("Enter the number");
        int num=Integer.parseInt(in.readLine());
    int sum=0;
    while(num>=0)
    {
      int rem=n;
      sum+=rem;
      int quo=n/10;
      n=quo;
    }
    System.out.println(sum);
  }
}

public class SumNatural {

    public static void main(String[] args) {

        int num = 100, sum = 0;

        for(int i = 1; i <= num; ++i)
        {
            // sum = sum + i;
            sum += i;
        }

        System.out.println("Sum = " + sum);
    }
}