Here is an example of how the Duration class from the logback library can be used:

import ch.qos.logback.core.util.Duration;

public class MyClass {
    public void myMethod() {
        Duration duration = new Duration(System.currentTimeMillis());
        // do some work
        long elapsedTime = duration.elapsedMillis();
        System.out.println("Elapsed time: " + elapsedTime + " milliseconds");
    }
}

In this example, MyClass uses an instance of Duration to measure the elapsed time between the creation of the Duration object and the call to the elapsedMillis method. The constructor of the Duration class takes a single argument, which is the start time in milliseconds.

You can also use elapsedNano to measure time in nano seconds, and computeDifference to calculate the difference between two durations.

Duration start = new Duration();
// do some work
Duration end = new Duration();
long diff = end.computeDifference(start);

This will return the difference between start and end in milliseconds.