Java时间常见转换

package time;

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

public class TestLocalDateTime {

private static final String TimeFormat="yyyy-MM-dd HH:mm:ss";
private static final String ZoneID="Asia/Shanghai";
public static void main(String[] args) {
    LocalDateTime now = LocalDateTime.now();
    //printTimeStr(now);
    //parseDataTime(now);
    LocalDateTime localDateTime = now.plusHours(1L);
    //parseDataTime(localDateTime);
    String s = printTimeStr(now);
    parseTimeStr(s);
}

public static void test01() {
    LocalDateTime now = LocalDateTime.now();
}

public static void test02() {
    // 当前时间
    LocalDateTime now = LocalDateTime.now();

// 5050年12月12日 14时30分 30秒 30纳秒 (秒和纳秒的部分可以省略)
LocalDateTime futureTime = LocalDateTime.of(5050, 12, 12, 14, 30, 30, 30);

// 添加: plus..() plusDays、plusMonth、plusYears...
LocalDateTime newTime_01 = now.plusDays(1); // 后一天

// 减少: minus..() minusDays、minusMonth、minusYears...
LocalDateTime newTime_02 = now.minusDays(1); // 前一天

// 设置各部分时间
LocalDateTime newYear = now.withYear(4040); // 改为4040年
LocalDateTime newMinute = now.withMinute(10); // 改为10月份
LocalDateTime newDay = now.withDayOfMonth(12); // 改为12日

// 通过字符串获取
String timeString = "5050-12-12 14:30";
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
LocalDateTime parseTime = LocalDateTime.parse(timeString, formatter);

    boolean isBefore = now.isBefore(newTime_01);
    boolean isAfter = now.isAfter(newTime_01);
    boolean isEqual = now.isEqual(newTime_01);
}

/**
 * 将字符串时间转换成时间戳
 * */

public static void parseTimeStr(String timeStr) {
    DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(TimeFormat);
    System.out.println(LocalDateTime.parse(timeStr, dateTimeFormatter).atZone(ZoneId.of(ZoneID)).toInstant().getEpochSecond());
}


public static void test04() {
    LocalDateTime now = LocalDateTime.now();
    // get..()   getHour、getMinute、getSecond...
    int year = now.getYear();
    Month month = now.getMonth(); // Month是枚举，返回值为月份的英文大写
    int hour = now.getHour();

// 其余同理
}

public static String printTimeStr(LocalDateTime dateTime) {
    DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(TimeFormat);
    String format = dateTimeFormatter.format(dateTime);
    System.out.println( DateTimeFormatter.ofPattern(TimeFormat).format(LocalDateTime.now()));
    System.out.println(format);
    return format;
}

public static void test05() {
    DateTimeFormatter format = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

    // 5050年12月12日 14时30分 30秒 30纳秒 (秒和纳秒的部分可以省略)
    LocalDateTime futureTime = LocalDateTime.of(5050, 12, 12, 14, 30, 30, 30);

// 转换为字符串
String timeString = format.format(futureTime);
// 字符串转换为LocalDateTime
LocalDateTime parseTime = LocalDateTime.parse(timeString, format);
}

/**
 * 将LocalDateTime转成时间错
 * */

public static void parseDataTime(LocalDateTime dateTime) {
    Instant instant = dateTime.atZone(ZoneId.of(ZoneID)).toInstant();
    long epochSecond = instant.getEpochSecond();
    System.out.println(epochSecond);
    System.out.println(instant.toEpochMilli());
    long now=System.currentTimeMillis();
    System.out.println(now/1000);
    System.out.println(now);
}

public static void test06() {
    LocalDateTime now = LocalDateTime.now();
    ZonedDateTime zonedDateTime = now.atZone(ZoneId.of("Asia/Shanghai"));
    Instant instant = zonedDateTime.toInstant();

    long milli = instant.toEpochMilli();     // 以毫秒为单位的时间戳
    long second = instant.getEpochSecond();  // 以秒为单位的时间戳

    // 以 毫秒 为单位的时间戳转为LocalDateTime
    LocalDateTime timeByMilli = Instant.ofEpochMilli(milli).atZone(ZoneId.of("Asia/Shanghai")).toLocalDateTime();

// 以 秒 为单位的时间戳转为LocalDateTime
LocalDateTime timeBySecond = Instant.ofEpochSecond(second).atZone(ZoneId.of("Asia/Shanghai")).toLocalDateTime();
// LocalDate、LocalTime同理
}

public static void test07() {

}

}