How to limit repainting to 75 hz in a Panel?

Question

Hello all, I have created a geometrical editor and I want to limit refresh rate of the repaints when I am moving an object on the screen to 75hz (or to the monitor refresh rate) because it uses 90% of CPU when moving an object.
When user drags an object I:
- detect it in the mouse listener (drag method)
- move the object in the memory (tree of objects)
- I call repaint of the panel
How can I enable t his limiting? I know there is some class called BufferStrategy, can I use something similar in JPanel? Or does this swing automatically? Thanks

Answer 1

Everybody gave you very good advices, but nobody
answer the question "how to limit to 75Hz ?" !
What is the best way to do this ? I don't know, but I
can give my own solution until a Java2D freak give
the ultimate one :
Create a framecounter
1)Create a counter : each time you execute the method
that render a frame, increase the counter.
2) in paint method, get the
System.currentTimeMillis(). Compare it with the last
value to compute de delta of time. Compare the
current framecounter value with the last value. You
have the delta of framecount. Compute framecount
delta over delta of time then multiply the result by
1000 to get the current framecount by seconds. If
result is over 75, paint method should return. Else
you call the method that render a frame.
What do you think about that ? I'm using this
solution, and it gives a quite good Fps control. Note
that I do not compute the curent Fps until an amount
of time is past. Exemple : I'm waiting for the delta
of time to reach about 300ms before computing delta
of framecount. That give a better current Fps average
but approximates the Fps control.
Have you a better method ?For timing that accurate you would need to use System.nanoTime().
Another way of achieving a framerate lock of 75 fps, is to change to a fullscreen mode, with a DisplayMode that is refreshing at 75hz, then create a BufferStrategy.
The BufferStrategy will be vsync locked (if the hardware driver allows vsync'ing), this will make BufferStrategy.show() block until the next vsync signal occurs.