Computing issue in writing program

I'm trying to write a quick test program that would add two number inclusively, let say one integer is 2 and the other is 7, I want it to comp开发者_运维技巧ute like this (2+3+4+5+6+7=27). Can't wrap my head around it.

Here is what I have

public class Test
{
    public static void main (String[] args)
    {
        int lo=2;
        int hi=7;

        int result=0;

        for(int i=lo;i<=hi;i++)
            result=i+i;

        System.out.println(result);
    }
}

You were close. I think you mean

result = result + i;

This basically means take the current value of result, add i to it, and then make result equal to that sum. This has the overall effect of adding i to result.

There's also a short-hand for _something_ = _something_ + _otherThing_, which in this case would look like:

result += i;

Use some math:

Sn = n/2 * (A1 + An),

where Sn is the sum of arithmetic progression of n elements with A1 as first element and An as last. See here.