It's a flag which determines whether or not to do an add operation or a subtract operation, and it is flipped* each time either is performed so that the two alternate. For Java you'd have to initialise the boolean to false, not 0.
*The ! inverts the boolean result of whatever follows it. So if "plus" is true, it will return false and vice versa.
I'm not really familiar with Java syntax, but from what randomizer said bool plus = 0 equivalent in Java should be:
boolean plus = false;
And as for i, it's declared in the loop at line 3:
int i = 0;
Finally, operator ! flips the boolean value, if it was true, it becomes false, and if it was false, it becomes true.
I was given the same task as ECSD, using the arcsine formula from the first post. Further info: when x=0.5 --> 6*arcsin(x) = Pi . That's how the formula might be incorporated. I'm completely new to Programming and I'm confused as to how to calculate to a power without using the Math.Class... I have the instructions to not use the Math.Class and to save the first 10000 digits of Pi in int-arrays.. any advice would be much appreciated