java.util.concurrent.TimeUnit以給定的粒度單位表示Java中的持續時間，并提供了跨單位轉換的實用方法。 java.util.concurrent.TimeUnit最早是在Java早期（1.5）引入的，但自那時以來已經被擴展了好幾次。 在此博客文章中，您將學習如何使用java.util.concurrent.TimeUnit將給定的時間單位轉換為持續時間 。

先決條件

您需要JDK 11+才能運行示例。

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問題

在Java中將給定的時間單位轉換為持續時間

解

使用java.concurrent.TimeUnit枚舉。

Java 11

• TimeUnit.convert(Duration duration) ：

long yearInMillis = TimeUnit.MILLISECONDS.convert(Duration.ofDays( 365 )); long hourInMillis = TimeUnit.MILLISECONDS.convert(Duration.ofHours( 1 )); long minuteInMillis = TimeUnit.MILLISECONDS.convert(Duration.ofMinutes( 1 ));

• 使用java.time.ChronoUnit TimeUnit.convert(Duration duration) ：

long yearInMillis = TimeUnit.MILLISECONDS.convert(Duration.of( 365 , TimeUnit.DAYS.toChronoUnit())); long hourInMillis = TimeUnit.MILLISECONDS.convert(Duration.of( 1 , TimeUnit.HOURS.toChronoUnit())); long minuteInMillis = TimeUnit.MILLISECONDS.convert(Duration.of( 1 , TimeUnit.MINUTES.toChronoUnit()));

Java 11之前的版本

• 通用TimeUnit.convert(long sourceDuration, TimeUnit sourceUnit)

long yearInMillis = TimeUnit.DAYS.toMillis( 365 ); long hourInMillis = TimeUnit.HOURS.toMillis( 1 ); long minuteInMillis = TimeUnit.MINUTES.toMillis( 1 );

• TimeUnit.toMillis(long duration) ， TimeUnit.toSeconds(long duration)等方法：

long yearInMillis = TimeUnit.MILLISECONDS.convert( 365 , TimeUnit.DAYS); long hourInMillis = TimeUnit.MILLISECONDS.convert( 1 , TimeUnit.HOURS); long minuteInMillis = TimeUnit.MILLISECONDS.convert( 1 , TimeUnit.MINUTES);

最后的例子

class Java11TimeUnitConvertTests { public static final long DAYS_IN_A_YEAR = 365L; public static final long HOURS_IN_A_DAY = 24L; public static final long MINUTES_IN_AN_HOUR = 60L; public static final long SECONDS_IN_A_MINUTE = 60L; public static final long MILLISECONDS_IN_A_SECOND = 1000L; @Test void aYearInMillis() { // A year in milliseconds long yearInMillis = TimeUnit.MILLISECONDS.convert(Duration.ofDays( 365 )); // since Java 11 assertThat(yearInMillis) .isEqualTo(DAYS_IN_A_YEAR * HOURS_IN_A_DAY * MINUTES_IN_AN_HOUR * SECONDS_IN_A_MINUTE * MILLISECONDS_IN_A_SECOND) .isEqualTo(TimeUnit.DAYS.toMillis( 365 )) .isEqualTo(TimeUnit.MILLISECONDS.convert( 365 , TimeUnit.DAYS)) .isEqualTo(TimeUnit.MILLISECONDS.convert(Duration.of( 365 , TimeUnit.DAYS.toChronoUnit()))); // since Java 11 } @Test void anHourInMillis() { long hourInMillis = TimeUnit.MILLISECONDS.convert(Duration.ofHours( 1 )); // since Java 11 ????????assertThat(hourInMillis) .isEqualTo(MINUTES_IN_AN_HOUR * SECONDS_IN_A_MINUTE * MILLISECONDS_IN_A_SECOND) .isEqualTo(TimeUnit.HOURS.toMillis( 1 )) .isEqualTo(TimeUnit.MILLISECONDS.convert( 1 , TimeUnit.HOURS)) .isEqualTo(TimeUnit.MILLISECONDS.convert(Duration.of( 1 , TimeUnit.HOURS.toChronoUnit()))); // since Java 11 } @Test void aMinuteInMillis() { ????????long minuteInMillis = TimeUnit.MILLISECONDS.convert(Duration.ofMinutes( 1 )); // since Java 11 ????????assertThat(minuteInMillis) .isEqualTo(SECONDS_IN_A_MINUTE * MILLISECONDS_IN_A_SECOND) .isEqualTo(TimeUnit.MINUTES.toMillis( 1 )) .isEqualTo(TimeUnit.MILLISECONDS.convert( 1 , TimeUnit.MINUTES)) .isEqualTo(TimeUnit.MILLISECONDS.convert(Duration.of( 1 , TimeUnit.MINUTES.toChronoUnit()))); // since Java 11 } @ParameterizedTest @MethodSource ( "timeUnitToDuration" ) void convertTimeUnitToDuration(TimeUnit unit, Duration duration, long expectedResult) { long actualResult = unit.convert(duration); assertThat(actualResult).isEqualTo(expectedResult); } private static Stream<Arguments> timeUnitToDuration() { return Stream.of( Arguments.of(TimeUnit.DAYS, Duration.ofHours( 24 ), 1 ), // 24h = 1d Arguments.of(TimeUnit.DAYS, Duration.ofHours( 40 ), 1 ), // 40h = 1d Arguments.of(TimeUnit.DAYS, Duration.ofHours( 48 ), 2 ), // 48h = 2d Arguments.of(TimeUnit.DAYS, Duration.ofHours( 50 ), 2 ), // 50h = 2d Arguments.of(TimeUnit.MILLISECONDS, Duration.ofSeconds( 1 ), 1000 ), // 1s = 1000ms Arguments.of(TimeUnit.MILLISECONDS, Duration.ofSeconds( 11 ), 11000 ), // 1s = 11000ms 11000 // 1s = 11000ms Arguments.of(TimeUnit.SECONDS, Duration.ofHours( 1 ), 3600 ), // 1h = 3600s Arguments.of(TimeUnit.HOURS, Duration.ofSeconds(4_000), 1 ), // 4000s = 1h Arguments.of(TimeUnit.HOURS, Duration.ofSeconds(1_0000), 2 ) // 10000s = 2h ); } }

源代碼

可以在Github上找到本文的源代碼： https : //github.com/kolorobot/java9-and-beyond

翻譯自: https://www.javacodegeeks.com/2020/05/convert-time-unit-to-duration-in-java.html

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