how to rotate a point around another point

Question

I am writing a game. I need to know how to rotate point a around point b by a given number of degrees. I am writing this in java and it is going to be part of my class, Point.

Answer 1

double x1 = point.x - center.x;
double y1 = point.y - center.y;

double x2 = x1 * Math.cos(angle) - y1 * Math.sin(angle));
double y2 = x1 * Math.sin(angle) + y1 * Math.cos(angle));

point.x = x2 + center.x;
point.y = y2 + center.y;

This approach uses rotation matrices. "point" is your point a, "center" is your point b.