Is there a method in Java 8 to make a Thread sleep until an Instant using a specific Clock?

Question

Given a Clock, an Instant and the current Thread, is there already some (utility) method in the Java libraries that makes the current thread sleep until the given clock reaches the instant?

Something like

public static void sleepUntil(Instant instant, Clock clock) 
 throws InterruptedException;

?

I need this in a test setting where I am working with a custom slowed-down clock.

I know that it is easy to implement, but I would prefer a standard solution if available (but didn't find it so far).

Answer 1

First of all, Clock is a really simple class with little implementation and few uses in the standard API. SystemClock, OffsetClock and TickClock are examples in the same file. So the answer seems to be No, it is not in the default API.

If you are given the "slowed-down clock" and may not modify it to add the desired sleepUntil()-code, and it is slowed down by a fixed amount, you could do something like

public static void sleepUntil(Instant instant, Clock clock) 
    throws InterruptedException {

    Instant now = Instant.now(clock);
    long duration = now.until(instant, ChronoUnit.MILLIS);
    long testSleep
        = ( duration < 10000 )? (duration / 10) : 1000;
    long start = clock.millis();
    Thread.sleep(testSleep);
    long stop = clock.millis();
    double clockskew = (stop - start) / testSleep;

    now = Instant.now(clock);
    Thread.sleep(now.until(instant, ChronoUnit.MILLIS) * clockskew);
}

This first does a test run to determine the clock skew, then sleeps an adjusted duration.

(Maybe you need to adjust the instant in sleep to adjust to the other clock. Post your clock code if you wish to have it tested/adjusted.)

Answer 2

In my case, I was needed to wait for a particular time. My solution.

long expirationTime = System.currentTimeMillis() + 60_000;
Thread.sleep(expirationTime - System.currentTimeMillis());

Another way is to do it with do-while but actually, I couldn't see its advantages.