Threads Question

I heard a question this week, and I thought it would be nice sharing it here, I did solve it, however, I'm not 100% sure I did it right :), so here it is:

What is the maximum value the variable i can get in each case below, assuming that it's a global int initialized by zero (int i=0) and the code in each case is running on 2 threads?

case1:

while(i < 1000)

{

    i++;

}

case2:

while(i < 1000)

{

    ++i;

}

case3:

while(i++ < 1000);

case4:

while(++i < 1000);