public class Test {

  public static void main(String[] args) {

    Date d = new Date();

    System.out.println(d); // 当前时间

    long time = d.getTime();

    System.out.println(time); // 当前时间的毫秒值

    time += 2 * 1000;

    Date d2 = new Date(time);

    System.out.println(d2);

    Date d3 = new Date();

    d3.setTime(time); // 设置当前时间

    System.out.println(d3);

  }

}

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Date;

public class Test {

  public static void main(String[] args) throws ParseException {

    Date d1 = new Date();

    long time = d1.getTime();

    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss EEE a");

    String rs1 = sdf.format(d1);

    System.out.println(rs1);

    String rs2 = sdf.format(time);

    System.out.println(rs2);

    // 指定的时间格式必须和被解析的时间格式一样，否则会出 bug

    String dateStr = "2024-08-27 04:16:00";

    SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    Date d2 = sdf2.parse(dateStr);

    System.out.println(d2);

  }

}

import java.util.Calendar;

import java.util.Date;

public class Test {

  public static void main(String[] args) {

    Calendar now = Calendar.getInstance();

    int year = now.get(Calendar.YEAR);

    System.out.println(year);

    Date date = now.getTime();

    System.out.println("日期对象：" + date);

    long time = now.getTimeInMillis();

    System.out.println("时间毫秒值：" + time);

    // 修改时间

    now.set(Calendar.YEAR, 2026);

    now.set(Calendar.MONTH, 5);

    now.set(Calendar.DAY_OF_YEAR, 6); // 修改成一年的第 6 天

    // 增加时间

    now.add(Calendar.DAY_OF_YEAR, 6);

    now.add(Calendar.DAY_OF_MONTH, 2);

  }

}

import java.time.LocalDate;

public class Test {

  public static void main(String[] args) {

    LocalDate d = LocalDate.now();

    System.out.println(d); // 2024-08-27

    int year = d.getYear(); // 2024

    LocalDate d2 = d.withYear(2026); // 2026-08-27

    LocalDate d3 = d.plusYears(4); // 2028-08-27

    LocalDate d4 = LocalDate.of(1988, 04, 16);

    System.out.println(d4.equals(d)); // false

    System.out.println(d4.isBefore(d)); // true

    System.out.println(d4.isAfter(d)); // false

  }

}

import java.time.Clock;

import java.time.ZoneId;

import java.time.ZonedDateTime;

public class Test {

  public static void main(String[] args) {

    // 获取系统默认的时区

    ZoneId zoneId = ZoneId.systemDefault();

    System.out.println(zoneId.getId()); // Asia/Shanghai

    System.out.println(ZoneId.getAvailableZoneIds()); // 获取全部时区 Id

    ZoneId zoneId2 = ZoneId.of("America/New_York");

    ZonedDateTime now = ZonedDateTime.now(zoneId2);

    System.out.println("美国纽约时区的时间：" + now);

    ZonedDateTime utc = ZonedDateTime.now(Clock.systemUTC());

    System.out.println("世界标准时间：" + utc);

    ZonedDateTime now2 = ZonedDateTime.now();

    System.out.println("系统默认时区的时间：" + now2);

    // Calendar instance = Calendar.getInstance(TimeZone.getTimeZone(zoneId));

  }

}

public class Test {

  public static void main(String[] args) {

    Instant now = Instant.now(); // 不可变对象

    long second = now.getEpochSecond(); // 总秒数

    int nano = now.getNano(); // 纳秒数

    Instant instant = now.plusNanos(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();

  }

}

public class Test {

  public static void main(String[] args) {

    LocalDate start = LocalDate.of(2024, 3, 5);

    LocalDate end = LocalDate.of(2029, 4, 16);

    Period between = Period.between(start, end);

    System.out.println("间隔年数：" + between.getYears()); // 间隔年数：5

    System.out.println("间隔月数：" + between.getMonths()); // 间隔月数：1

    System.out.println("间隔天数：" + between.getDays()); // 间隔天数：11

  }

}

import java.time.Duration;

import java.time.LocalDateTime;

public class Test {

  public static void main(String[] args) {

    LocalDateTime start = LocalDateTime.of(2024, 8, 28, 11, 10, 10);

    LocalDateTime end = LocalDateTime.of(2024, 8, 28, 11, 11, 11);

    Duration between = Duration.between(start, end);

    System.out.println(between.toDays()); // 0

    System.out.println(between.toHours()); // 0

    System.out.println(between.toMinutes()); // 1

    System.out.println(between.toSeconds()); // 61

    System.out.println(between.toMillis()); // 61000

    System.out.println(between.toNanos()); // 61000000000

  }

}