Know this is late, but this simple question has been unanswered for too long.
The call to System.out.println, which is an expensive operation, is performed every time the mouse is dragged. Every position change will print a line. The faster a position changes the faster it will print.
Deleting this print call should fix the problem and make the console info more useful.
A minimum difference condition to allow the call to print could also solve the problem.

The call to System.out.println, which is an expensive operation, is performed every time the mouse is dragged. Every position change will print a line. The faster a position changes the faster it will print.

Deleting this print call should fix the problem and make the console info more useful.

A minimum difference condition to allow the call to print could also solve the problem.