datetime - How to get milliseconds from LocalDateTime in Java 8

Datetime - How to get milliseconds from LocalDateTime in Java 8

In Java 8, LocalDateTime does not directly support milliseconds. However, you can get milliseconds from a LocalDateTime by converting it to a java.time.Instant and then extracting the milliseconds from the Instant object. Here's how you can do it:

import java.time.LocalDateTime; import java.time.Instant; public class Main { public static void main(String[] args) { // Create a LocalDateTime object LocalDateTime localDateTime = LocalDateTime.now(); // Convert LocalDateTime to Instant Instant instant = localDateTime.atZone(java.time.ZoneId.systemDefault()).toInstant(); // Get milliseconds from Instant long milliseconds = instant.toEpochMilli(); // Print milliseconds System.out.println("Milliseconds: " + milliseconds); } }

In this example:

  • We create a LocalDateTime object representing the current date and time.
  • We convert the LocalDateTime object to an Instant using the atZone method and specifying the system's default time zone.
  • We extract the milliseconds from the Instant using the toEpochMilli method.

This way, you can get the milliseconds from a LocalDateTime object in Java 8.

Examples

  1. How to convert LocalDateTime to milliseconds since epoch in Java 8?

    • Description: This query focuses on converting a LocalDateTime object to milliseconds since the epoch (January 1, 1970, 00:00:00 GMT).
    • Code:
      import java.time.LocalDateTime; import java.time.ZoneId; import java.time.ZonedDateTime; public class Main { public static void main(String[] args) { LocalDateTime localDateTime = LocalDateTime.now(); long milliseconds = localDateTime .atZone(ZoneId.systemDefault()) .toInstant() .toEpochMilli(); System.out.println("Milliseconds since epoch: " + milliseconds); } }

  2. Extract milliseconds from LocalDateTime in Java 8

    • Description: This query involves extracting the millisecond component from a LocalDateTime object.
    • Code:
      import java.time.LocalDateTime; import java.time.temporal.ChronoField; public class Main { public static void main(String[] args) { LocalDateTime localDateTime = LocalDateTime.now(); int milliseconds = localDateTime.get(ChronoField.MILLI_OF_SECOND); System.out.println("Milliseconds: " + milliseconds); } }

  3. Convert LocalDateTime to Instant and get milliseconds in Java 8

    • Description: This query explains how to convert a LocalDateTime to an Instant and then get the milliseconds.
    • Code:
      import java.time.Instant; import java.time.LocalDateTime; import java.time.ZoneId; public class Main { public static void main(String[] args) { LocalDateTime localDateTime = LocalDateTime.now(); Instant instant = localDateTime.atZone(ZoneId.systemDefault()).toInstant(); long milliseconds = instant.toEpochMilli(); System.out.println("Milliseconds since epoch: " + milliseconds); } }

  4. Get current time in milliseconds from LocalDateTime in Java 8

    • Description: This query focuses on getting the current time in milliseconds from a LocalDateTime object.
    • Code:
      import java.time.LocalDateTime; import java.time.ZoneId; public class Main { public static void main(String[] args) { LocalDateTime localDateTime = LocalDateTime.now(); long milliseconds = localDateTime .atZone(ZoneId.systemDefault()) .toInstant() .toEpochMilli(); System.out.println("Current milliseconds since epoch: " + milliseconds); } }

  5. Convert LocalDateTime to milliseconds using ZoneOffset in Java 8

    • Description: This query demonstrates converting a LocalDateTime to milliseconds using a specified ZoneOffset.
    • Code:
      import java.time.LocalDateTime; import java.time.ZoneOffset; public class Main { public static void main(String[] args) { LocalDateTime localDateTime = LocalDateTime.now(); long milliseconds = localDateTime .toInstant(ZoneOffset.UTC) .toEpochMilli(); System.out.println("Milliseconds since epoch (UTC): " + milliseconds); } }

  6. How to get epoch milliseconds from LocalDateTime in specific time zone in Java 8?

    • Description: This query focuses on getting the epoch milliseconds from a LocalDateTime in a specific time zone.
    • Code:
      import java.time.LocalDateTime; import java.time.ZoneId; public class Main { public static void main(String[] args) { LocalDateTime localDateTime = LocalDateTime.now(); ZoneId zoneId = ZoneId.of("America/New_York"); long milliseconds = localDateTime .atZone(zoneId) .toInstant() .toEpochMilli(); System.out.println("Milliseconds since epoch (New York): " + milliseconds); } }

  7. Calculate milliseconds from LocalDateTime using Clock in Java 8

    • Description: This query involves using the Clock class to calculate milliseconds from a LocalDateTime.
    • Code:
      import java.time.Clock; import java.time.LocalDateTime; import java.time.ZoneId; import java.time.ZonedDateTime; public class Main { public static void main(String[] args) { Clock clock = Clock.systemDefaultZone(); LocalDateTime localDateTime = LocalDateTime.now(clock); long milliseconds = localDateTime .atZone(clock.getZone()) .toInstant() .toEpochMilli(); System.out.println("Milliseconds since epoch: " + milliseconds); } }

  8. Convert LocalDateTime to milliseconds using ZonedDateTime in Java 8

    • Description: This query explains how to convert LocalDateTime to milliseconds using ZonedDateTime.
    • Code:
      import java.time.LocalDateTime; import java.time.ZoneId; import java.time.ZonedDateTime; public class Main { public static void main(String[] args) { LocalDateTime localDateTime = LocalDateTime.now(); ZonedDateTime zonedDateTime = localDateTime.atZone(ZoneId.systemDefault()); long milliseconds = zonedDateTime.toInstant().toEpochMilli(); System.out.println("Milliseconds since epoch: " + milliseconds); } }

  9. How to get milliseconds of the day from LocalDateTime in Java 8

    • Description: This query focuses on getting the number of milliseconds that have passed since the start of the day from a LocalDateTime object.
    • Code:
      import java.time.LocalDateTime; import java.time.temporal.ChronoField; public class Main { public static void main(String[] args) { LocalDateTime localDateTime = LocalDateTime.now(); long millisecondsOfDay = localDateTime.getLong(ChronoField.MILLI_OF_DAY); System.out.println("Milliseconds of the day: " + millisecondsOfDay); } }

  10. Get milliseconds difference between two LocalDateTime instances in Java 8

    • Description: This query demonstrates calculating the milliseconds difference between two LocalDateTime instances.
    • Code:
      import java.time.Duration; import java.time.LocalDateTime; public class Main { public static void main(String[] args) { LocalDateTime start = LocalDateTime.of(2023, 1, 1, 0, 0); LocalDateTime end = LocalDateTime.now(); long milliseconds = Duration.between(start, end).toMillis(); System.out.println("Milliseconds difference: " + milliseconds); } }

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