计算机的时间处理

时间戳

1.LocalDate转Date

LocalDate nowLocalDate = LocalDate.now();
Date date = Date.from(localDate.atStartOfDay(ZoneOffset.ofHours(8)).toInstant());

2.LocalDateTime转Date

LocalDateTime localDateTime = LocalDateTime.now();
Date date = Date.from(localDateTime.atZone(ZoneOffset.ofHours(8)).toInstant());

3.Date转LocalDateTime(LocalDate)

Date date =newDate();
LocalDateTime localDateTime = date.toInstant().atZone(ZoneOffset.ofHours(8)).toLocalDateTime();
LocalDate localDate = date.toInstant().atZone(ZoneOffset.ofHours(8)).toLocalDate();

4.LocalDate转时间戳

LocalDate localDate = LocalDate.now();
longtimestamp = localDate.atStartOfDay(ZoneOffset.ofHours(8)).toInstant().toEpochMilli();

5.LocalDateTime转时间戳

LocalDateTime localDateTime = LocalDateTime.now();
longtimestamp = localDateTime.toInstant(ZoneOffset.ofHours(8)).toEpochMilli();

6.时间戳转LocalDateTime(LocalDate)

longtimestamp = System.currentTimeMillis();
LocalDate localDate = Instant.ofEpochMilli(timestamp).atZone(ZoneOffset.ofHours(8)).toLocalDate();
LocalDateTime localDateTime = Instant.ofEpochMilli(timestamp).atZone(ZoneOffset.ofHours(8)).toLocalDateTime();

获取标准时间

package com.lv.study.pm.first;

public class TestMil {

    public static void main(String[] args) {

        
        //想要获取我们标准时刻；现在距离1970年1.1 00:00:00多少毫秒
        //java获取标准时刻
        
        //1 获取时刻
        System.out.println(System.currentTimeMillis());
        long it=System.currentTimeMillis();
        
        //2 距离标准时刻过了多少秒
        System.out.println(it/1000);
        
        //3  过了多少个分钟
        System.out.println(it/1000/60);
        
        //4 过了多少小时
        System.out.println(it/1000/60/60);
        
        //5 过了多少天
        System.out.println(it/1000/60/60/24);
        
        //6 过了多少年
        System.out.println(it/1000/60/60/24/365);
        
    }

}

　　

方法2

package com.lv.study.pm.first;

import java.text.SimpleDateFormat;
import java.util.Date;

public class TestSimpleDateFormat {

    public static void main(String[] args) {

        test2();
        
    }
    
    public static void test2(){
        //只要符合 yyyy MM  dd HH mm  ss的规则就可以的
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
        
        System.out.println(sdf.format(new Date()));
    }
    
    public static void test1(){

        //针对java.util.Date 做一个格式化输出
        
        //以指定的格式输出日期
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        
        //new Date()当前日期
        String sdate=sdf.format(new Date());
        
        System.out.println(sdate);
    }

}

方法3

package com.lv.study.pm.second;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;

public class TestLocalDate {

    public static void main(String[] args) {
        
        //只负责日期，不负责时间只负责年月日
        LocalDate ld=LocalDate.now();
        
        System.out.println(ld.getYear());
        System.out.println(ld.getMonth());
        System.out.println(ld.getMonthValue());
        System.out.println(ld.getDayOfMonth());
        
        //只负责时间不负责日期
        LocalTime it=LocalTime.now();
        System.out.println(it.getHour());


        //都负责
        LocalDateTime ldt=LocalDateTime.now();
        System.out.println(ldt.getDayOfYear());
        
    }
}