Triangle number with 500 divisors
Java is a just-in-time compiled language. As a side-effect of this, it is common for performance problems to happen when you have all the code in the main method. The reason is that Java often only compiles methods that are called very often, but the main method is only called once, so it is not compiled optimally.

This is one reason why 'function extraction' is often suggested (as well as the other benefits like readability).

So, consider a method that's called 'countDivisors':

private static long countDivisors(long value) {
    long count = 1;
    for (long i = 1; i &lt;= value/2; i++) {
        if (value % i == 0) {
            count++;
        }
    }
    return count;
}


This code will be called often, and will thus be compiled optimally.

The main method also becomes simpler, with:

public static void main(String args[]){
    long count = 1, sum = 0, i = 0;
    do {
        i++;
        sum += i
        count = countDivisors(sum);
    } while (count &lt; 500);
    System.out.println(i);
}


Now, whether this improves the performance enough, is uncertain, but it is more readable, and will be faster.

There's probably a smarter way to do this too, a better algorithm is normally what's required with Euler problems.