Java 8 中 Date與LocalDateTime、LocalDate、LocalTime互轉
阿新 • • 發佈:2018-12-22
Java 8中 java.util.Date 類新增了兩個方法,分別是from(Instant instant)和toInstant()方法
// Obtains an instance of Date from an Instant object. public static Date from(Instant instant) { try { return new Date(instant.toEpochMilli()); } catch (ArithmeticException ex) { throw new IllegalArgumentException(ex); } } // Converts this Date object to an Instant. public Instant toInstant() { return Instant.ofEpochMilli(getTime()); }
這兩個方法使我們可以方便的實現將舊的日期類轉換為新的日期類,具體思路都是通過Instant當中介,然後通過Instant來建立LocalDateTime(這個類可以很容易獲取LocalDate和LocalTime),新的日期類轉舊的也是如此,將新的先轉成LocalDateTime,然後獲取Instant,接著轉成Date,具體實現細節如下:
// 01. java.util.Date --> java.time.LocalDateTime public void UDateToLocalDateTime() { java.util.Date date = new java.util.Date(); Instant instant = date.toInstant(); ZoneId zone = ZoneId.systemDefault(); LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone); } // 02. java.util.Date --> java.time.LocalDate public void UDateToLocalDate() { java.util.Date date = new java.util.Date(); Instant instant = date.toInstant(); ZoneId zone = ZoneId.systemDefault(); LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone); LocalDate localDate = localDateTime.toLocalDate(); } // 03. java.util.Date --> java.time.LocalTime public void UDateToLocalTime() { java.util.Date date = new java.util.Date(); Instant instant = date.toInstant(); ZoneId zone = ZoneId.systemDefault(); LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone); LocalTime localTime = localDateTime.toLocalTime(); } // 04. java.time.LocalDateTime --> java.util.Date public void LocalDateTimeToUdate() { LocalDateTime localDateTime = LocalDateTime.now(); ZoneId zone = ZoneId.systemDefault(); Instant instant = localDateTime.atZone(zone).toInstant(); java.util.Date date = Date.from(instant); } // 05. java.time.LocalDate --> java.util.Date public void LocalDateToUdate() { LocalDate localDate = LocalDate.now(); ZoneId zone = ZoneId.systemDefault(); Instant instant = localDate.atStartOfDay().atZone(zone).toInstant(); java.util.Date date = Date.from(instant); } // 06. java.time.LocalTime --> java.util.Date public void LocalTimeToUdate() { LocalTime localTime = LocalTime.now(); LocalDate localDate = LocalDate.now(); LocalDateTime localDateTime = LocalDateTime.of(localDate, localTime); ZoneId zone = ZoneId.systemDefault(); Instant instant = localDateTime.atZone(zone).toInstant(); java.util.Date date = Date.from(instant); }