+1 to the interface being to complex, I've also suggested dropping about 1/3 of it.
Not sure about using a common interface though: I don't think the wallClock-related methods are as many as the ones for cpu time (actually I think we should only have a single wallClock method that returns the current time as we don't need/barely need any interval/duration comparisons on wallClock). Also the cpu time is in nanos whilst the wall clock is in millis, and that should be documented at the interface level (unless we return some composite objects containing the time unit as well, much to complicated)