If you have a Java 8 Clock, then you can use clock.millis() (although it recommends you use clock.instant() to get a Java 8 Instant, as it's more accurate).
Why would you use a Java 8 clock? So in your DI framework you can create a Clock bean:
@Bean
public Clock getClock() {
return Clock.systemUTC();
}
and then in your tests you can easily Mock it:
@MockBean private Clock clock;
or you can have a different bean:
@Bean
public Clock getClock() {
return Clock.fixed(instant, zone);
}
which helps with tests that assert dates and times immeasurably.