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Java Clock millis()

By Arvind Rai, May 20, 2019
Java Clock.millis gets the current millisecond instant of the clock. millis method returns the millisecond-based instant measured from 1970-01-01T00:00Z (UTC). millis is equivalent to the definition of System.currentTimeMillis(). To get an instant on the time-line, we should use Instant instead of millis. According to Java, we should use millis only in high performance use-cases where the creation of an object would be unacceptable.
Find the declaration of Clock.millis from Java doc.
public long millis() 
The above method will return millisecond instant from this clock.




Now find the examples.
Example-1: We are instantiating clock with default zone and then calling millis on this clock.
MillisDefaultZone.java
package com.concretepage;
import java.time.Clock;
public class MillisDefaultZone {
  public static void main(String[] args) {
	Clock clock = Clock.systemDefaultZone();
	long millis = clock.millis();
	System.out.println(millis);
  }
} 
Output
1558345581477 
Example-2: We are instantiating clock with given zone i.e. Asia/Calcutta and then calling millis on this clock.
MillisSpecifiedZone.java
package com.concretepage;
import java.time.Clock;
import java.time.ZoneId;
public class MillisSpecifiedZone {
  public static void main(String[] args) {
	ZoneId zone = ZoneId.of("Asia/Calcutta");   
	Clock clock = Clock.system(zone);
	long millis = clock.millis();
	System.out.println(millis);
  }
} 
Output
1558345649093 
Example-3: We are instantiating clock using Clock.systemUTC. It returns the clock that gives current instant using UTC time-zone. Now we are calling millis on this clock.
MillisSystemUTC.java
package com.concretepage;
import java.time.Clock;
public class MillisSystemUTC {
  public static void main(String[] args) {
	Clock clock = Clock.systemUTC();
	long millis = clock.millis();
	System.out.println(millis);
  }
} 
Output
1558345693056 
Example-4: We are instantiating clock using Clock.fixed. It returns a fixed clock that always gives the same instant. Now we are calling millis on this clock.
MillisFixed.java
package com.concretepage;
import java.time.Clock;
import java.time.Instant;
import java.time.ZoneId;
public class MillisFixed {
  public static void main(String[] args) {
	Instant instant = Instant.parse("2019-05-18T15:34:42.00Z");
	ZoneId zoneId = ZoneId.of("Asia/Calcutta");
	Clock clock = Clock.fixed(instant, zoneId);

	for (int i = 1; i <= 3; i++) {
	  System.out.println("-----" + i + "-----");
	  System.out.println(clock.millis());
	  try {
		Thread.sleep(2000);
	  } catch (InterruptedException e) {
		e.printStackTrace();
	  }
	}
  }
} 
Output
-----1-----
1558193682000
-----2-----
1558193682000
-----3-----
1558193682000 

References

Java Doc: Class Clock
Java Clock
POSTED BY
ARVIND RAI
ARVIND RAI
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