DateTimeFormatter 时间戳和String类型日期

代码如下:

import java.time.LocalDateTime;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;

public class ceshi {
public static void main(String[] args) {
    String num="2020-05-29 14:06:51.577";
    long zhi=strTimestamp(num);
    System.out.println("string转为时间戳:"+zhi);
    String a=timeToStr(zhi);
    System.out.println("时间戳转为string:"+a);
}
public static long strTimestamp(String str) {
    long time;
    String pattern="yyyy-MM-dd HH:mm:ss.SSS";
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern(pattern);
    LocalDateTime localDateTime=LocalDateTime.parse(str,formatter);
    time=localDateTime.toInstant(ZoneOffset.ofHours(12)).toEpochMilli();
    return time;
}
public static String timeToStr(long num) {
    String time="";
    String pattern="yyyy-MM-dd HH:mm:ss.SSS";
    LocalDateTime dateTime = LocalDateTime.ofEpochSecond(num/1000L, 0, ZoneOffset.ofHours(12));
     time = dateTime.format(DateTimeFormatter.ofPattern(pattern));
    return time;
}
}

输出结果:

string转为时间戳:1590718011577
时间戳转为string:2020-05-29 14:06:51.000

如需按8小时制，修改12为8即可。