知识的领域是无限的,我们的学习也是无限期的。这篇文章主要讲述Java 新的日期时间 API#yyds干货盘点#相关的知识，希望能为你提供帮助。
java 新的日期时间 APIJava8提供了如下几个时间API
| 时间相关类 | 介绍 |
|---|---|
| LocalDateTime | 时间处理类，最高精确到纳秒 |
| LocalDate | 时间处理类，最高精确到天 |
| DateTimeFormatter | 时间格式化 |
| ZoneId | 时区设置类 |
public static void main(String[] args) throws Exception {
String str = "20201231121212";
String pattern = "yyyyMMddHHmmss";
long res1 = new SimpleDateFormat(pattern).parse(str).getTime();
System.out.println(res1);
LocalDateTime ldt = LocalDateTime.parse(str, DateTimeFormatter.ofPattern(pattern));
Long newSecond = ldt.toEpochSecond(ZoneOffset.of("+8")) * 1000;
System.out.println(newSecond);
}结果：
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示例：时间戳转日期类型的字符串
public static String long2str(long dateLong, String pattern) {
LocalDateTime ldt =LocalDateTime.ofInstant(Instant.ofEpochMilli(dateLong), ZoneId.systemDefault());
String res = ldt.format(DateTimeFormatter.ofPattern(pattern));
return res;
}
public static void main(String[] args) throws Exception {
String str = "20201231121212";
String pattern = "yyyyMMddHHmmss";
long longTime = new SimpleDateFormat(pattern).parse(str).getTime();
System.out.println(longTime);
String res = long2str(longTime, pattern);
System.out.println(res);
}示例1 ：获取当前时间
@Test
public void testNowTime() {
// 获取当前日期
LocalDate localDate = LocalDate.now();
System.out.println("当前日期：" + localDate);
System.out.println("当前日期：" + localDate.getYear() + "-" + localDate.getMonthValue() + "-" + localDate.getDayOfMonth());
// 获取当天时间
LocalTime localTime = LocalTime.now();
System.out.println("当天时间：" + localTime);
System.out.println("当天时间：" + localTime.getHour() + ":" + localTime.getMinute() + ":" + localTime.getSecond());
// 当前精确时间
LocalDateTime now = LocalDateTime.now();
System.out.println("当前精确时间：" + now);
System.out.println("当前精确时间：" + now.getYear() + "-" + now.getMonthValue() + "-" + now.getDayOfMonth() + " " + now.getHour() + "-" + now.getMinute() + "-" + now.getSecond());
// 有时区的当前精确时间
ZonedDateTime nowZone = LocalDateTime.now().atZone(ZoneId.systemDefault());
System.out.println("当前精确时间（有时区）：" + nowZone);
System.out.println("当前精确时间（有时区）：" + nowZone.getYear() + "-" + nowZone.getMonthValue() + "-" + nowZone.getDayOfMonth() + " " + nowZone.getHour() + "-" + nowZone.getMinute() + "-" + nowZone.getSecond());
}结果：
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示例2：创建指定的本地化日期时间
@Test
public void dateAPI() {
LocalDate localDate = LocalDate.of(1999,9,21);
System.out.println(localDate);
System.out.println(localDate.getYear());
System.out.println(localDate.getMonth());
System.out.println(localDate.getDayOfMonth());
LocalDate localDateParse = LocalDate.parse("1840-01-01");
System.out.println(localDateParse.getYear());
LocalTime localTime = LocalTime.of(3, 20);
System.out.println(localTime);
System.out.println(localTime.getHour());
System.out.println(localTime.getMinute());
LocalTime localTimeParse = LocalTime.parse("11:35");
System.out.println(localTimeParse.getHour());
LocalDateTime localDateTime1 = LocalDateTime.of(1999, 9, 21, 12, 12, 12);
System.out.println(localDateTime1);
LocalDateTime localDateTime = LocalDateTime.now();
System.out.println(localDateTime);
LocalDate localDate1 = localDateTime.toLocalDate();
System.out.println(localDate1);
LocalTime localTime1 = localDateTime.toLocalTime();
System.out.println(localTime1);
LocalDateTime localDateTimeParse = LocalDateTime.parse("2999-09-21T11:44:11");
System.out.println(localDateTimeParse.getMinute());
}示例3：使用时区的日期时间API：ZoneId 、ZonedDateTime
@Test
public void zonedDateTime(){
ZoneId currentZone = ZoneId.systemDefault();
System.out.println("当期时区: " + currentZone);
// 获取当前时间日期
ZonedDateTime date1 = ZonedDateTime.parse("2015-12-03T10:15:30+05:30[Asia/Shanghai]");
System.out.println("date1: " + date1);
LocalDateTime localDateTime = LocalDateTime.now(ZoneId.of("Asia/Shanghai"));
System.out.println(localDateTime);
LocalDateTime localDateTime11 = LocalDateTime.now(ZoneId.of("Europe/Paris"));
System.out.println(localDateTime11);
}示例4：时间格式化
@Test
public void testFormat() {
LocalDateTime now = LocalDateTime.now();
System.out.println("当前时间：" + now);
System.out.println("格式化后：" + now.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME));
System.out.println("格式化后：" + now.format(DateTimeFormatter.ISO_LOCAL_DATE));
System.out.println("格式化后：" + now.format(DateTimeFormatter.ISO_LOCAL_TIME));
System.out.println("格式化后：" + now.format(DateTimeFormatter.ofPattern("YYYY-MM-dd hh:mm:ss")));
}DateTimeFormatter除了可以格式化
结果：
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示例5：时间比较
@Test
public void testComp() {
LocalDateTime now = LocalDateTime.now();
LocalDateTime after = LocalDateTime.of(1999,9,21,12,12,12);
System.out.println(now.equals(after));
// isEqual：如果比较的日期为空，则会抛出异常
System.out.println(now.isEqual(after));
System.out.println(now + " 在 " + after + " 之后吗？ " + now.isAfter(after));
System.out.println(now + " 在 " + after + " 之前吗？ " + now.isBefore(after));
// 时间差
long day = after.until(now, ChronoUnit.DAYS);
System.out.println("相差天数: " + day);
long month = after.until(now, ChronoUnit.MONTHS);
System.out.println("相差月份: " + month);
long hours = after.until(now, ChronoUnit.HOURS);
System.out.println("相差小时: " + hours);
long minutes = after.until(now, ChronoUnit.MINUTES);
System.out.println("相差分钟: " + minutes);
// 距离JDK 14 发布还有多少天？
LocalDate jdk14 = LocalDate.of(2020, 11, 17);
LocalDate nowDate = LocalDate.now();
System.out.println("距离JDK 14 发布还有：" + nowDate.until(jdk14, ChronoUnit.DAYS) + "天");
}结果：
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示例6：时间加减
@Test
public void testCalculate() {
LocalDateTime now = LocalDateTime.now();
System.out.println("当前时间是："+now);
LocalDateTime plusTime = now.plusMonths(1).plusDays(2).plusHours(12).plusMinutes(12).plusSeconds(12);
System.out.println("增加1月2天12小时12分钟12秒时间后：" + plusTime);
LocalDateTime minusTime = now.minusMonths(2);
System.out.println("减少2个月时间后：" + minusTime);
}【Java 新的日期时间 API#yyds干货盘点#】结果：
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示例7：其它方法
@Test
public void timeFunctionTest() {
LocalDateTime now = LocalDateTime.now();
System.out.println("当前时间：" + now);
// 第十天
LocalDateTime firstDay = now.withDayOfMonth(10);
System.out.println("本月第一天：" + firstDay);
// 最后一天
LocalDateTime lastDay = now.with(TemporalAdjusters.lastDayOfMonth());
System.out.println("本月最后一天:" + lastDay);
// 是否闰年
System.out.println("今年是否闰年：" + Year.isLeap(now.getYear()));
}结果
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新旧日期转换：（了解会用就行，不要求掌握）示例3：java.util.Date 转 java.time.LocalDateTime
public LocalDateTime date2LocalDateTime(Date date) {
Instant instant = date.toInstant();
ZoneId zone = ZoneId.systemDefault();
LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone);
returnlocalDateTime;
}示例4：java.util.Date 转 java.time.LocalDate
public LocalDate date2LocalDate(Date date) {
Instant instant = date.toInstant();
ZoneId zone = ZoneId.systemDefault();
LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone);
LocalDate localDate = localDateTime.toLocalDate();
return localDate;
}示例5：java.util.Date 转 java.time.LocalTime
public LocalTime date2LocalTime(Date date) {
Instant instant = date.toInstant();
ZoneId zone = ZoneId.systemDefault();
LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone);
LocalTime localTime = localDateTime.toLocalTime();
return localTime;
}
示例6：java.time.LocalDateTime 转 java.util.Date
public Date LocalDateTime2Date(LocalDateTime localDateTime) {
ZoneId zone = ZoneId.systemDefault();
Instant instant = localDateTime.atZone(zone).toInstant();
Date date = Date.from(instant);
return date;
}示例7： java.time.LocalDate转 java.util.Date
public Date LocalDate2Date(LocalDate localDate) {
ZoneId zone = ZoneId.systemDefault();
Instant instant = localDate.atStartOfDay().atZone(zone).toInstant();
Date date = Date.from(instant);
return date;
}示例8： java.time.LocalTime转 java.util.Date
public Date LocalTime2Date(LocalTime localTime) {
LocalDate localDate = LocalDate.now();
LocalDateTime localDateTime = LocalDateTime.of(localDate, localTime);
ZoneId zone = ZoneId.systemDefault();
Instant instant = localDateTime.atZone(zone).toInstant();
Date date = Date.from(instant);
return date;
}示例9：获取时间戳
public static void main(String[] args) {
//获取当前时间戳
final long epochMilli = Instant.now().toEpochMilli();
System.out.println(epochMilli);
// 通过时间戳生成当前时间（东八区）
final LocalDateTime localDateTime = Instant.ofEpochMilli(epochMilli)
.atZone(ZoneOffset.ofHours(8))
.toLocalDateTime();
System.out.println(localDateTime);
}结果：
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