Java LocalTime
LocalTime 是 Java 8 引入的時間類別，用於表示不含日期的時間（時、分、秒、奈秒），位於 java.time 套件中。
引入套件
import java.time.LocalTime;
建立 LocalTime
取得當前時間
LocalTime now = LocalTime.now();
System.out.println(now); // 14:30:45.123456789
指定時間
// of(時, 分)
LocalTime time1 = LocalTime.of(14, 30);
System.out.println(time1); // 14:30
// of(時, 分, 秒)
LocalTime time2 = LocalTime.of(14, 30, 45);
System.out.println(time2); // 14:30:45
// of(時, 分, 秒, 奈秒)
LocalTime time3 = LocalTime.of(14, 30, 45, 123456789);
System.out.println(time3); // 14:30:45.123456789
從字串解析
LocalTime time = LocalTime.parse("14:30:45");
System.out.println(time); // 14:30:45
// 自訂格式
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("HH:mm:ss");
LocalTime time2 = LocalTime.parse("14:30:45", formatter);
特殊常數
LocalTime midnight = LocalTime.MIDNIGHT; // 00:00
LocalTime noon = LocalTime.NOON; // 12:00
LocalTime min = LocalTime.MIN; // 00:00
LocalTime max = LocalTime.MAX; // 23:59:59.999999999
取得時間資訊
LocalTime time = LocalTime.of(14, 30, 45, 123456789);
int hour = time.getHour(); // 14
int minute = time.getMinute(); // 30
int second = time.getSecond(); // 45
int nano = time.getNano(); // 123456789
// 轉換為當天的秒數
int secondOfDay = time.toSecondOfDay(); // 52245
// 轉換為當天的奈秒數
long nanoOfDay = time.toNanoOfDay();
時間運算
加減時間
LocalTime time = LocalTime.of(14, 30, 0);
// 加上時間
LocalTime plus2Hours = time.plusHours(2); // 16:30
LocalTime plus30Mins = time.plusMinutes(30); // 15:00
LocalTime plus30Secs = time.plusSeconds(30); // 14:30:30
LocalTime plusNanos = time.plusNanos(1000000); // 14:30:00.001
// 減去時間
LocalTime minus1Hour = time.minusHours(1); // 13:30
LocalTime minus15Mins = time.minusMinutes(15); // 14:15
跨午夜處理
LocalTime time = LocalTime.of(23, 30);
LocalTime newTime = time.plusHours(2);
System.out.println(newTime); // 01:30（自動回到次日凌晨）
LocalTime time2 = LocalTime.of(1, 0);
LocalTime earlier = time2.minusHours(3);
System.out.println(earlier); // 22:00（自動回到前一天晚上）
修改時間
LocalTime time = LocalTime.of(14, 30, 45);
LocalTime newHour = time.withHour(10); // 10:30:45
LocalTime newMinute = time.withMinute(0); // 14:00:45
LocalTime newSecond = time.withSecond(0); // 14:30:00
LocalTime newNano = time.withNano(0); // 14:30:45
時間比較
LocalTime time1 = LocalTime.of(14, 30);
LocalTime time2 = LocalTime.of(16, 0);
boolean isBefore = time1.isBefore(time2); // true
boolean isAfter = time1.isAfter(time2); // false
boolean equals = time1.equals(time2); // false
int result = time1.compareTo(time2); // 負數（time1 較早）
計算時間差距
LocalTime start = LocalTime.of(9, 0);
LocalTime end = LocalTime.of(17, 30);
// 使用 Duration
Duration duration = Duration.between(start, end);
long hours = duration.toHours(); // 8
long minutes = duration.toMinutes(); // 510
// 使用 ChronoUnit
long hoursBetween = ChronoUnit.HOURS.between(start, end); // 8
long minutesBetween = ChronoUnit.MINUTES.between(start, end); // 510
long secondsBetween = ChronoUnit.SECONDS.between(start, end); // 30600
格式化輸出
LocalTime time = LocalTime.of(14, 30, 45);
// 預設格式
System.out.println(time.toString()); // 14:30:45
// 自訂格式
DateTimeFormatter formatter1 = DateTimeFormatter.ofPattern("HH:mm:ss");
System.out.println(time.format(formatter1)); // 14:30:45
DateTimeFormatter formatter2 = DateTimeFormatter.ofPattern("hh:mm a");
System.out.println(time.format(formatter2)); // 02:30 PM
DateTimeFormatter formatter3 = DateTimeFormatter.ofPattern("H時m分s秒");
System.out.println(time.format(formatter3)); // 14時30分45秒
轉換為其他類型
LocalTime time = LocalTime.of(14, 30, 45);
LocalDate date = LocalDate.of(2024, 12, 25);
// 結合日期建立 LocalDateTime
LocalDateTime dateTime = time.atDate(date); // 2024-12-25T14:30:45
// 從秒數建立
LocalTime fromSeconds = LocalTime.ofSecondOfDay(52245); // 14:30:45
// 從奈秒數建立
LocalTime fromNanos = LocalTime.ofNanoOfDay(52245000000000L);
時間截斷
LocalTime time = LocalTime.of(14, 30, 45, 123456789);
// 截斷到小時
LocalTime truncatedToHour = time.truncatedTo(ChronoUnit.HOURS); // 14:00
// 截斷到分鐘
LocalTime truncatedToMinute = time.truncatedTo(ChronoUnit.MINUTES); // 14:30
// 截斷到秒
LocalTime truncatedToSecond = time.truncatedTo(ChronoUnit.SECONDS); // 14:30:45
實用範例
判斷營業時間
public static boolean isBusinessHours(LocalTime time) {
LocalTime open = LocalTime.of(9, 0);
LocalTime close = LocalTime.of(18, 0);
return !time.isBefore(open) && time.isBefore(close);
}
System.out.println(isBusinessHours(LocalTime.of(10, 30))); // true
System.out.println(isBusinessHours(LocalTime.of(20, 0))); // false
計算工作時數
public static String calculateWorkHours(LocalTime clockIn, LocalTime clockOut) {
Duration duration = Duration.between(clockIn, clockOut);
long hours = duration.toHours();
long minutes = duration.toMinutesPart();
return hours + "小時" + minutes + "分鐘";
}
LocalTime in = LocalTime.of(9, 0);
LocalTime out = LocalTime.of(18, 30);
System.out.println(calculateWorkHours(in, out)); // 9小時30分鐘
時間區間判斷
public static boolean isInTimeRange(LocalTime time, LocalTime start, LocalTime end) {
if (start.isBefore(end)) {
// 正常區間（如 09:00 - 18:00）
return !time.isBefore(start) && time.isBefore(end);
} else {
// 跨午夜區間（如 22:00 - 06:00）
return !time.isBefore(start) || time.isBefore(end);
}
}
// 夜班時間判斷
LocalTime nightStart = LocalTime.of(22, 0);
LocalTime nightEnd = LocalTime.of(6, 0);
System.out.println(isInTimeRange(LocalTime.of(23, 0), nightStart, nightEnd)); // true
System.out.println(isInTimeRange(LocalTime.of(3, 0), nightStart, nightEnd)); // true
System.out.println(isInTimeRange(LocalTime.of(12, 0), nightStart, nightEnd)); // false
格式化為 12 小時制
public static String formatTo12Hour(LocalTime time) {
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("hh:mm a", Locale.ENGLISH);
return time.format(formatter);
}
System.out.println(formatTo12Hour(LocalTime.of(14, 30))); // 02:30 PM
System.out.println(formatTo12Hour(LocalTime.of(9, 15))); // 09:15 AM
重點整理
LocalTime表示不含日期的時間（時:分:秒.奈秒）- 是不可變（immutable）類別
- 使用
now()取得當前時間 - 使用
of()建立指定時間 - 跨午夜運算會自動處理（回繞到 0-24 小時範圍）
- 使用
Duration或ChronoUnit計算時間差距 - 搭配
DateTimeFormatter可格式化為各種格式