I am new bee into the world of Datastructures and algorithms from ground up. This is my attempt to learn.

If the question is very plain/simple . Please bear with me.

Problem:

Find the sum of all the multiples of 3 or 5 below 1000.

Code i worte:

package problem1;

public class Problem1 {

    public static void main(String[] args) {


        //******************Approach 1****************
        long start = System.currentTimeMillis();
        int total = 0;
        int toSubtract = 0;

        //Complexity N/3
        int limit = 10000;      
        for(int i=3 ; i<limit ;i=i+3){
            total = total +i;
        }

        //Complexity N/5
        for(int i=5 ; i<limit ;i=i+5){
            total = total +i;
        }       

        //Complexity N/15
        for(int i=15 ; i<limit ;i=i+15){
            toSubtract = toSubtract +i;
        }           
        //9N/15   = 0.6 N
        System.out.println(total-toSubtract);
        System.out.println("Completed in "+(System.currentTimeMillis() - start));


        //******************Approach 2****************
        for(int i=3 ; i<limit ;i=i+3){
            total = total +i;
        }

        for(int i=5 ; i<limit ;i=i+5){          
            if ( 0 != (i%3)) total = total +i;
        }

    }


}

Question 1 - Which best approach from the above code and why ? 2 - Are there any better alternatives ?