在 Java 中优雅地操纵时间

public class Date {
    long fastTime;

    public Date(long date) {
        fastTime = date;
    }

    public long getTime() {
        return fastTime;
    }
}

import java.util.*;

public class Main {
    public static void main(String[] args) {
        // 获取当前时间:
        Calendar c = Calendar.getInstance();
        int y = c.get(Calendar.YEAR);//返回年份不用转换
        int m = 1 + c.get(Calendar.MONTH);//返回月份需要加1
        int d = c.get(Calendar.DAY_OF_MONTH);
        int w = c.get(Calendar.DAY_OF_WEEK);//返回的
        int hh = c.get(Calendar.HOUR_OF_DAY);
        int mm = c.get(Calendar.MINUTE);
        int ss = c.get(Calendar.SECOND);
        int ms = c.get(Calendar.MILLISECOND);
        System.out.println(y + "-" + m + "-" + d + " " + w + " " + hh + ":" + mm + ":" + ss + "." + ms);
    }
}

import java.text.*;
import java.util.*;

public class Main {
    public static void main(String[] args) {
        // 当前时间:
        Calendar c = Calendar.getInstance();
        // 清除所有:
        c.clear();
        // 设置年月日时分秒:
        c.set(2019, 10 /* 11月 */, 20, 8, 15, 0);
        // 加5天并减去2小时:
        c.add(Calendar.DAY_OF_MONTH, 5);
        c.add(Calendar.HOUR_OF_DAY, -2);
        // 显示时间:
        var sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Date d = c.getTime();
        System.out.println(sdf.format(d));
        // 2019-11-25 6:15:00
    }
}

import java.text.*;
import java.util.*;

public class learnTime {
    public static void main(String[] args) {
        // 当前时间:
        Calendar c = Calendar.getInstance();
        // 清除所有字段:
        c.clear();
        // 设置为北京时区:
        c.setTimeZone(TimeZone.getTimeZone("Asia/Shanghai"));
        // 设置年月日时分秒:
        c.set(2024, 9 /* 10月 */, 10, 8, 15, 0);
        // 显示时间:
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        sdf.setTimeZone(TimeZone.getTimeZone("America/New_York"));
        System.out.println(sdf.format(c.getTime()));
        // 2024-10-09 20:15:00
    }
}

// SimpleDateFormat线程不安全，每次使用都要构造新的，在初始的时候定义解析的字符串格式
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

// 将指定字符串String解析为Date
Date date = format.parse("2024-10-07 16:10:22");

// 将Date格式化为String
String str = format.format(date);

static final ThreadLocal<SimpleDateFormat> SIMPLE_DATE_FORMAT_LOCAL 
    = ThreadLocal.withInitial(
        () -> new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
);

//1、创建Instant的对象，获取此刻时间信息
Instant now = Instant.now(); //不可变对象
//2、获取总秒数
long second = now.getEpochSecond();
system.out.println(second) ;
//3、不够1秒的纳秒数
int nano = now.getNano();
system.out.println(nano) ;

system.out.println(now);
//可以进行加减法 
Instant instant = now.plusNanos(111);//将纳秒加111

// Instant对象的作用:做代码的性能分析，或者记录用户的操作时间点
Instant now1 = Instant.now();
//代码执行...
Instant now2 = Instant.now();
//用这两个时间点相减就可以知道这段代码运行了多少时间

import java.time.*;
import java.time.format.*;
import java.util.Locale;

public class Main {
    public static void main(String[] args) {
        ZonedDateTime zdt = ZonedDateTime.now();
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm ZZZZ");
        System.out.println(formatter.format(zdt));

        DateTimeFormatter zhFormatter = DateTimeFormatter.ofPattern("yyyy MMM dd EE HH:mm", Locale.CHINA);
        System.out.println(zhFormatter.format(zdt));

        DateTimeFormatter usFormatter = DateTimeFormatter.ofPattern("E, MMMM/dd/yyyy HH:mm", Locale.US);
        System.out.println(usFormatter.format(zdt));

        //2024-10-08T00:25 GMT+08:00
        //2024 十月 08 星期二 00:25
        //Tue, October/08/2024 00:25
    }
}

// LocalDateTime 转换为 Date
LocalDateTime localDateTime = LocalDateTime.now();
ZonedDateTime zonedDateTime = localDateTime.atZone(ZoneId.systemDefault());
Date date = Date.from(zonedDateTime.toInstant());
// Date 转换为 LocalDateTime
Date date = new Date();
Instant instant = date.toInstant();
LocalDateTime localDateTime = instant.atZone(ZoneId.systemDefault()).toLocalDateTime();

import java.time.*;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;

public class DateUtils {

    // 获取当前日期
    public static LocalDate getCurrentDate() {
        return LocalDate.now();
    }

    // 获取当前时间
    public static LocalTime getCurrentTime() {
        return LocalTime.now();
    }

    // 获取当前日期时间
    public static LocalDateTime getCurrentDateTime() {
        return LocalDateTime.now();
    }

    // 格式化日期为字符串
    public static String formatLocalDate(LocalDate date, String pattern) {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern(pattern);
        return date.format(formatter);
    }

    // 解析字符串为LocalDate
    public static LocalDate parseLocalDate(String dateStr, String pattern) {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern(pattern);
        return LocalDate.parse(dateStr, formatter);
    }

    // 增加指定天数
    public static LocalDate addDays(LocalDate date, long days) {
        return date.plusDays(days);
    }

    // 减少指定天数
    public static LocalDate minusDays(LocalDate date, long days) {
        return date.minusDays(days);
    }

    // 计算两个日期之间的天数差
    public static long getDaysBetween(LocalDate startDate, LocalDate endDate) {
        return ChronoUnit.DAYS.between(startDate, endDate);
    }

    // 获取指定日期所在月份的第一天
    public static LocalDate getFirstDayOfMonth(LocalDate date) {
        return date.withDayOfMonth(1);
    }

    // 获取指定日期所在月份的最后一天
    public static LocalDate getLastDayOfMonth(LocalDate date) {
        return date.withDayOfMonth(date.lengthOfMonth());
    }

    // 判断两个日期是否相等
    public static boolean isSameDate(LocalDate date1, LocalDate date2) {
        return date1.isEqual(date2);
    }

    // 判断日期是否在指定范围内
    public static boolean isDateInRange(LocalDate date, LocalDate startDate, LocalDate endDate) {
        return date.isAfter(startDate) && date.isBefore(endDate);
    }

    // 获取指定日期的星期几
    public static DayOfWeek getDayOfWeek(LocalDate date) {
        return date.getDayOfWeek();
    }

    // 判断是否为闰年
    public static boolean isLeapYear(int year) {
        return Year.of(year).isLeap();
    }

    // 获取指定月份的天数
    public static int getDaysInMonth(int year, int month) {
        return YearMonth.of(year, month).lengthOfMonth();
    }

    // 获取指定日期的年份
    public static int getYear(LocalDate date) {
        return date.getYear();
    }

    // 获取指定日期的月份
    public static int getMonth(LocalDate date) {
        return date.getMonthValue();
    }

    // 获取指定日期的天数
    public static int getDayOfMonth(LocalDate date) {
        return date.getDayOfMonth();
    }

    // 获取指定日期的小时数
    public static int getHour(LocalDateTime dateTime) {
        return dateTime.getHour();
    }

    // 获取指定日期的分钟数
    public static int getMinute(LocalDateTime dateTime) {
        return dateTime.getMinute();
    }

    // 获取指定日期的秒数
    public static int getSecond(LocalDateTime dateTime) {
        return dateTime.getSecond();
    }

    // 判断指定日期是否在当前日期之前
    public static boolean isBefore(LocalDate date) {
        return date.isBefore(LocalDate.now());
    }

    // 判断指定日期是否在当前日期之后
    public static boolean isAfter(LocalDate date) {
        return date.isAfter(LocalDate.now());
    }

    // 判断指定日期是否在当前日期之前或相等
    public static boolean isBeforeOrEqual(LocalDate date) {
        return date.isBefore(LocalDate.now()) || date.isEqual(LocalDate.now());
    }

    // 判断指定日期是否在当前日期之后或相等
    public static boolean isAfterOrEqual(LocalDate date) {
        return date.isAfter(LocalDate.now()) || date.isEqual(LocalDate.now());
    }

    // 获取指定日期的年龄
    public static int getAge(LocalDate birthDate) {
        LocalDate currentDate = LocalDate.now();
        return Period.between(birthDate, currentDate).getYears();
    }

    // 获取指定日期的季度
    public static int getQuarter(LocalDate date) {
        return (date.getMonthValue() - 1) / 3 + 1;
    }

    // 获取指定日期的下一个工作日
    public static LocalDate getNextWorkingDay(LocalDate date) {
        do {
            date = date.plusDays(1);
        } while (date.getDayOfWeek() == DayOfWeek.SATURDAY || date.getDayOfWeek() == DayOfWeek.SUNDAY);
        return date;
    }

    // 获取指定日期的上一个工作日
    public static LocalDate getPreviousWorkingDay(LocalDate date) {
        do {
            date = date.minusDays(1);
        } while (date.getDayOfWeek() == DayOfWeek.SATURDAY || date.getDayOfWeek() == DayOfWeek.SUNDAY);
        return date;
    }

    // 获取指定日期所在周的第一天（周一）
    public static LocalDate getFirstDayOfWeek(LocalDate date) {
        return date.with(DayOfWeek.MONDAY);
    }

    // 获取指定日期所在周的最后一天（周日）
    public static LocalDate getLastDayOfWeek(LocalDate date) {
        return date.with(DayOfWeek.SUNDAY);
    }

    // 获取指定日期所在年的第一天
    public static LocalDate getFirstDayOfYear(LocalDate date) {
        return date.withDayOfYear(1);
    }

    // 获取指定日期所在年的最后一天
    public static LocalDate getLastDayOfYear(LocalDate date) {
        return date.withDayOfYear(date.lengthOfYear());
    }

    // 获取指定日期所在季度的第一天
    public static LocalDate getFirstDayOfQuarter(LocalDate date) {
        int month = (date.getMonthValue() - 1) / 3 * 3 + 1;
        return LocalDate.of(date.getYear(), month, 1);
    }

    // 获取指定日期所在季度的最后一天
    public static LocalDate getLastDayOfQuarter(LocalDate date) {
        int month = (date.getMonthValue() - 1) / 3 * 3 + 3;
        return LocalDate.of(date.getYear(), month, Month.of(month).maxLength());
    }

    // 判断指定日期是否为工作日（周一至周五）
    public static boolean isWeekday(LocalDate date) {
        return date.getDayOfWeek() != DayOfWeek.SATURDAY && date.getDayOfWeek() != DayOfWeek.SUNDAY;
    }

    // 判断指定日期是否为周末（周六或周日）
    public static boolean isWeekend(LocalDate date) {
        return date.getDayOfWeek() == DayOfWeek.SATURDAY || date.getDayOfWeek() == DayOfWeek.SUNDAY;
    }

    // 获取指定日期所在月份的工作日天数
    public static int getWeekdayCountOfMonth(LocalDate date) {
        int weekdayCount = 0;
        LocalDate firstDayOfMonth = getFirstDayOfMonth(date);
        LocalDate lastDayOfMonth = getLastDayOfMonth(date);

        while (!firstDayOfMonth.isAfter(lastDayOfMonth)) {
            if (isWeekday(firstDayOfMonth)) {
                weekdayCount++;
            }
            firstDayOfMonth = firstDayOfMonth.plusDays(1);
        }

        return weekdayCount;
    }

    // 获取指定日期所在月份的周末天数
    public static int getWeekendCountOfMonth(LocalDate date) {
        int weekendCount = 0;
        LocalDate firstDayOfMonth = getFirstDayOfMonth(date);
        LocalDate lastDayOfMonth = getLastDayOfMonth(date);

        while (!firstDayOfMonth.isAfter(lastDayOfMonth)) {
            if (isWeekend(firstDayOfMonth)) {
                weekendCount++;
            }
            firstDayOfMonth = firstDayOfMonth.plusDays(1);
        }

        return weekendCount;
    }

    // 获取指定日期所在年份的工作日天数
    public static int getWeekdayCountOfYear(LocalDate date) {
        int weekdayCount = 0;
        LocalDate firstDayOfYear = getFirstDayOfYear(date);
        LocalDate lastDayOfYear = getLastDayOfYear(date);

        while (!firstDayOfYear.isAfter(lastDayOfYear)) {
            if (isWeekday(firstDayOfYear)) {
                weekdayCount++;
            }
            firstDayOfYear = firstDayOfYear.plusDays(1);
        }

        return weekdayCount;
    }

}