What is the difference between Callback<T> and Java 8's Supplier<T>?
- by Dan Pantry
I've been switching over to Java from C# after some recommendations from some over at CodeReview. So, when I was looking into LWJGL, one thing I remembered was that every call to Display must be executed on the same thread that the Display.create() method was invoked on. Remembering this, I whipped up a class that looks a bit like this.
public class LwjglDisplayWindow implements DisplayWindow {
private final static int TargetFramesPerSecond = 60;
private final Scheduler _scheduler;
public LwjglDisplayWindow(Scheduler displayScheduler, DisplayMode displayMode) throws LWJGLException {
_scheduler = displayScheduler;
Display.setDisplayMode(displayMode);
Display.create();
}
public void dispose() {
Display.destroy();
}
@Override
public int getTargetFramesPerSecond() { return TargetFramesPerSecond; }
@Override
public Future<Boolean> isClosed() {
return _scheduler.schedule(() -> Display.isCloseRequested());
}
}
While writing this class you'll notice that I created a method called isClosed() that returns a Future<Boolean>. This dispatches a function to my Scheduler interface (which is nothing more than a wrapper around an ScheduledExecutorService. While writing the schedule method on the Scheduler I noticed that I could either use a Supplier<T> argument or a Callable<T> argument to represent the function that is passed in. ScheduledExecutorService didn't contain an override for Supplier<T> but I noticed that the lambda expression () -> Display.isCloseRequested() is actually type compatible with both Callable<bool> and Supplier<bool>.
My question is, is there a difference between those two, semantically or otherwise - and if so, what is it, so I can adhere to it?
