日期、包装类、正则表达式朗姆大
获取系统时间毫秒值可以用System.currentTimeMillis()，更快更简单。
import javax.xml.crypto.Data;
import java.util.Calendar;
import java.util.Date;
/**
目标：日历类Calendar的使用,可以得到更加丰富的信息。
Calendar代表了系统此刻日期对应的日历对象。
Calendar是一个抽象类，不能直接创建对象。
Calendar日历类创建日历对象的语法：
Calendar rightNow = Calendar.getInstance();
Calendar的方法：
1.public static Calendar getInstance(): 返回一个日历类的对象。
2.public int get(int field)：取日期中的某个字段信息。
3.public void set(int field,int value)：修改日历的某个字段信息。
4.public void add(int field,int amount)：为某个字段增加/减少指定的值
5.public final Date getTime(): 拿到此刻日期对象。
6.public long getTimeInMillis(): 拿到此刻时间毫秒值
小结：
记住。
*/
public class CalendarDemo{
public static void main(String[] args) {
// 1、拿到系统此刻日历对象
Calendar cal = Calendar.getInstance();
System.out.println(cal);
// 2、获取日历的信息:public int get(int field)：取日期中的某个字段信息。
int year = cal.get(Calendar.YEAR);
System.out.println(year);
int mm = cal.get(Calendar.MONTH) + 1;
System.out.println(mm);
int days = cal.get(Calendar.DAY_OF_YEAR) ;
System.out.println(days);
// 3、public void set(int field,int value)：修改日历的某个字段信息。
// cal.set(Calendar.HOUR , 12);
// System.out.println(cal);
// 4.public void add(int field,int amount)：为某个字段增加/减少指定的值
// 请问64天后是什么时间
cal.add(Calendar.DAY_OF_YEAR , 64);
cal.add(Calendar.MINUTE , 59);
// 5.public final Date getTime(): 拿到此刻日期对象。
Date d = cal.getTime();
System.out.println(d);
// 6.public long getTimeInMillis(): 拿到此刻时间毫秒值
long time = cal.getTimeInMillis();
System.out.println(time);
}
}
public class Demo02LocalTime {
public static void main(String[] args) {
// 1、获取本地时间对象。
LocalTime nowTime = LocalTime.now();
System.out.println("今天的时间：" + nowTime);//今天的时间：
int hour = nowTime.getHour();//时
System.out.println("hour：" + hour);//hour：
int minute = nowTime.getMinute();//分
System.out.println("minute：" + minute);//minute：
int second = nowTime.getSecond();//秒
System.out.println("second：" + second);//second：
int nano = nowTime.getNano();//纳秒
System.out.println("nano：" + nano);//nano：
System.out.println("-----");
System.out.println(LocalTime.of(8, 20));//时分
System.out.println(LocalTime.of(8, 20, 30));//时分秒
System.out.println(LocalTime.of(8, 20, 30, 150));//时分秒纳秒
LocalTime mTime = LocalTime.of(8, 20, 30, 150);
System.out.println("---------------");
System.out.println(LocalDateTime.of(1991, 11, 11, 8, 20));
System.out.println(LocalDateTime.of(1991, Month.NOVEMBER, 11, 8, 20));
System.out.println(LocalDateTime.of(1991, 11, 11, 8, 20, 30));
System.out.println(LocalDateTime.of(1991, Month.NOVEMBER, 11, 8, 20, 30));
System.out.println(LocalDateTime.of(1991, 11, 11, 8, 20, 30, 150));
System.out.println(LocalDateTime.of(1991, Month.NOVEMBER, 11, 8, 20, 30, 150));
}
public class Demo01LocalDate {
public static void main(String[] args) {
// 1、获取本地日期对象。
LocalDate nowDate = LocalDate.now();
System.out.println("今天的日期：" + nowDate);//今天的日期：
int year = nowDate.getYear();
System.out.println("year：" + year);
int month = nowDate.getMonthValue();
System.out.println("month：" + month);
int day = nowDate.getDayOfMonth();
System.out.println("day：" + day);
//当年的第几天
int dayOfYear = nowDate.getDayOfYear();
System.out.println("dayOfYear：" + dayOfYear);
//星期
System.out.println(nowDate.getDayOfWeek());
System.out.println(nowDate.getDayOfWeek().getValue());
//月份
System.out.println(nowDate.getMonth());//AUGUST
System.out.println(nowDate.getMonth().getValue());//8
System.out.println("------------------------");
LocalDate bt = LocalDate.of(1991, 11, 11);
System.out.println(bt);//直接传入对应的年月日
System.out.println(LocalDate.of(1991, Month.NOVEMBER, 11));//相对上面只是把月换成了枚举
}
}
public class Demo03LocalDateTime {
public static void main(String[] args) {
// 日期 时间
LocalDateTime nowDateTime = LocalDateTime.now();
System.out.println("今天是：" + nowDateTime);//今天是：
System.out.println(nowDateTime.getYear());//年
System.out.println(nowDateTime.getMonthValue());//月
System.out.println(nowDateTime.getDayOfMonth());//日
System.out.println(nowDateTime.getHour());//时
System.out.println(nowDateTime.getMinute());//分
System.out.println(nowDateTime.getSecond());//秒
System.out.println(nowDateTime.getNano());//纳秒
//日：当年的第几天
System.out.println("dayOfYear：" + nowDateTime.getDayOfYear());//dayOfYear：249
//星期
System.out.println(nowDateTime.getDayOfWeek());//THURSDAY
System.out.println(nowDateTime.getDayOfWeek().getValue());//4
//月份
System.out.println(nowDateTime.getMonth());//SEPTEMBER
System.out.println(nowDateTime.getMonth().getValue());//9
LocalDate ld = nowDateTime.toLocalDate();
System.out.println(ld);
LocalTime lt = nowDateTime.toLocalTime();
System.out.println(lt.getHour());
System.out.println(lt.getMinute());
System.out.println(lt.getSecond());
}
}
public class Demo04UpdateTime {
public static void main(String[] args) {
LocalTime nowTime = LocalTime.now();
System.out.println(nowTime);//当前时间
System.out.println(nowTime.minusHours(1));//一小时前
System.out.println(nowTime.minusMinutes(1));//一分钟前
System.out.println(nowTime.minusSeconds(1));//一秒前
System.out.println(nowTime.minusNanos(1));//一纳秒前
System.out.println("----------------");
System.out.println(nowTime.plusHours(1));//一小时后
System.out.println(nowTime.plusMinutes(1));//一分钟后
System.out.println(nowTime.plusSeconds(1));//一秒后
System.out.println(nowTime.plusNanos(1));//一纳秒后
System.out.println("------------------");
// 不可变对象，每次修改产生新对象！
System.out.println(nowTime);
System.out.println("---------------");
LocalDate myDate = LocalDate.of(2018, 9, 5);
LocalDate nowDate = LocalDate.now();
System.out.println("今天是2018-09-06吗？ " + nowDate.equals(myDate));//今天是2018-09-06吗？ false
System.out.println(myDate + "是否在" + nowDate + "之前？ " + myDate.isBefore(nowDate));//2018-09-05是否在2018-09-06之前？ true
System.out.println(myDate + "是否在" + nowDate + "之后？ " + myDate.isAfter(nowDate));//2018-09-05是否在2018-09-06之后？ false
System.out.println("---------------------------");
// 判断今天是否是你的生日
LocalDate birDate = LocalDate.of(1996, 8, 5);
LocalDate nowDate1 = LocalDate.now();
MonthDay birMd = MonthDay.of(birDate.getMonthValue(), birDate.getDayOfMonth());
MonthDay nowMd = MonthDay.from(nowDate1);
System.out.println("今天是你的生日吗？ " + birMd.equals(nowMd));//今天是你的生日吗？ false
}
}
public class Demo05Instant {
public static void main(String[] args) {
// 1、得到一个Instant时间戳对象
Instant instant = Instant.now();
System.out.println(instant);
// 2、系统此刻的时间戳怎么办？
Instant instant1 = Instant.now();
System.out.println(instant1.atZone(ZoneId.systemDefault()));
// 3、如何去返回Date对象
Date date = Date.from(instant);
System.out.println(date);
Instant i2 = date.toInstant();
System.out.println(i2);
}
}
public class Demo06DateTimeFormat {
public static void main(String[] args) {
// 本地此刻 日期时间 对象
LocalDateTime ldt = LocalDateTime.now();
System.out.println(ldt);
// 解析/格式化器
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss EEE a");
// 正向格式化
System.out.println(dtf.format(ldt));
// 逆向格式化
System.out.println(ldt.format(dtf));
// 解析字符串时间
DateTimeFormatter dtf1 = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
// 解析当前字符串时间成为本地日期时间对象
LocalDateTime ldt1 = LocalDateTime.parse("2019-11-11 11:11:11" , dtf1);
System.out.println(ldt1);
System.out.println(ldt1.getDayOfYear());
}
}
public class Demo07Period {
public static void main(String[] args) {
// 当前本地 年月日
LocalDate today = LocalDate.now();
System.out.println(today);//
// 生日的 年月日
LocalDate birthDate = LocalDate.of(1998, 10, 13);
System.out.println(birthDate);
Period period = Period.between(birthDate, today);//第二个参数减第一个参数
System.out.println(period.getYears());
System.out.println(period.getMonths());
System.out.println(period.getDays());
}
}
public class Demo08Duration {
public static void main(String[] args) {
// 本地日期时间对象。
LocalDateTime today = LocalDateTime.now();
System.out.println(today);
// 出生的日期时间对象
LocalDateTime birthDate = LocalDateTime.of(2021,8
,06,01,00,00);
System.out.println(birthDate);
Duration duration = Duration.between( today , birthDate);//第二个参数减第一个参数
System.out.println(duration.toDays());//两个时间差的天数
System.out.println(duration.toHours());//两个时间差的小时数
System.out.println(duration.toMinutes());//两个时间差的分钟数
System.out.println(duration.toMillis());//两个时间差的毫秒数
System.out.println(duration.toNanos());//两个时间差的纳秒数
}
}
public class Demo09ChronoUnit {
public static void main(String[] args) {
// 本地日期时间对象：此刻的
LocalDateTime today = LocalDateTime.now();
System.out.println(today);
// 生日时间
LocalDateTime birthDate = LocalDateTime.of(1990,10,1,
10,50,59);
System.out.println(birthDate);
System.out.println("相差的年数：" + ChronoUnit.YEARS.between(birthDate, today));
System.out.println("相差的月数：" + ChronoUnit.MONTHS.between(birthDate, today));
System.out.println("相差的周数：" + ChronoUnit.WEEKS.between(birthDate, today));
System.out.println("相差的天数：" + ChronoUnit.DAYS.between(birthDate, today));
System.out.println("相差的时数：" + ChronoUnit.HOURS.between(birthDate, today));
System.out.println("相差的分数：" + ChronoUnit.MINUTES.between(birthDate, today));
System.out.println("相差的秒数：" + ChronoUnit.SECONDS.between(birthDate, today));
System.out.println("相差的毫秒数：" + ChronoUnit.MILLIS.between(birthDate, today));
System.out.println("相差的微秒数：" + ChronoUnit.MICROS.between(birthDate, today));
System.out.println("相差的纳秒数：" + ChronoUnit.NANOS.between(birthDate, today));
System.out.println("相差的半天数：" + ChronoUnit.HALF_DAYS.between(birthDate, today));
System.out.println("相差的十年数：" + ChronoUnit.DECADES.between(birthDate, today));
System.out.println("相差的世纪（百年）数：" + ChronoUnit.CENTURIES.between(birthDate, today));
System.out.println("相差的千年数：" + ChronoUnit.MILLENNIA.between(birthDate, today));
System.out.println("相差的纪元数：" + ChronoUnit.ERAS.between(birthDate, today));
}
}
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