Largest prime factor program takes aaaages - Java

Question

So this is problem 3 from project Euler. For those who don\'t know, I have to find out the largest prime factor of 600851475143. I have the below code:

impor         


        

Answer 1

change

for(long i = 2; i <= limit; i++)

to

// add the one for rounding errors in the sqrt function
new_limit = sqrt(limit) + 1;
// all even numbers are not prime 
for(long i = 3; i <= new_limit; i+=2)
{
...
}

Factoring 1,000,000 for example instead of iterating 1,000,000 times the thing only needs to do around 500 iterations.