The sum of the squares of the first ten natural numbers is,
1^2 + 2^2 + … + 10^2 = 385The square of the sum of the first ten natural numbers is,
(1 + 2 + … + 10)^2 = 55^2 = 3025Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is
3025 – 385 = 2640.Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum.
Running time: 0ms
Assessment: I exhibited symptoms of brain inversion the first time I read the problem description. I was very tired when I wrote this. How do I know? There are zombies in my code. 
public class Problem006
{
private static long sum_squares(int n)
{
int total = 0;
for (int i = 1; i <= n; i++)
total += (i*i);
System.out.println("sum_squares() = " + total);
return total;
}
private static long squares_sum(int n)
{
long total = 0;
for (int i = 1; i <= n; i++)
total += i;
total *= total;
System.out.println("squares_sum() = " + total);
return total;
}
public static void main(String args[])
{
long begin = System.currentTimeMillis();
long omg_zombies = squares_sum(100) - sum_squares(100);
long end = System.currentTimeMillis();
System.out.println(omg_zombies);
System.out.println(end-begin + "ms");
}
}
solution in java for project euler problem 6
public class problem6
 {
 public static void main(String args[])
 {
int total = 0;
        int tot=0;
        int diff=0;
        for (int i = 1; i <= 100; i++)
        {
total += (i*i);
            tot+=i;
        diff=(tot*tot)-total;
       Â
        }
System.out.println("sum_squares() = " + total);
        System.out.println("squares_sum() = " + tot);
         System.out.println("difference= " + diff);
}
}