计算机的时间处理

时间戳

 1 1.LocalDate转Date
 2 
 3 LocalDate nowLocalDate = LocalDate.now();
 4 Date date = Date.from(localDate.atStartOfDay(ZoneOffset.ofHours(8)).toInstant());
 5 
 6 2.LocalDateTime转Date
 7 
 8 LocalDateTime localDateTime = LocalDateTime.now();
 9 Date date = Date.from(localDateTime.atZone(ZoneOffset.ofHours(8)).toInstant());
10 
11 3.Date转LocalDateTime(LocalDate)
12 
13 Date date =newDate();
14 LocalDateTime localDateTime = date.toInstant().atZone(ZoneOffset.ofHours(8)).toLocalDateTime();
15 LocalDate localDate = date.toInstant().atZone(ZoneOffset.ofHours(8)).toLocalDate();
16 
17 4.LocalDate转时间戳
18 
19 LocalDate localDate = LocalDate.now();
20 longtimestamp = localDate.atStartOfDay(ZoneOffset.ofHours(8)).toInstant().toEpochMilli();
21 
22 5.LocalDateTime转时间戳
23 
24 LocalDateTime localDateTime = LocalDateTime.now();
25 longtimestamp = localDateTime.toInstant(ZoneOffset.ofHours(8)).toEpochMilli();
26 
27 6.时间戳转LocalDateTime(LocalDate)
28 
29 longtimestamp = System.currentTimeMillis();
30 LocalDate localDate = Instant.ofEpochMilli(timestamp).atZone(ZoneOffset.ofHours(8)).toLocalDate();
31 LocalDateTime localDateTime = Instant.ofEpochMilli(timestamp).atZone(ZoneOffset.ofHours(8)).toLocalDateTime();

获取标准时间

 1 package com.lv.study.pm.first;
 2 
 3 public class TestMil {
 4 
 5     public static void main(String[] args) {
 6 
 7         
 8         //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
 9         //java获取标准时刻
10         
11         //1 获取时刻
12         System.out.println(System.currentTimeMillis());
13         long it=System.currentTimeMillis();
14         
15         //2 距离标准时刻过了多少秒
16         System.out.println(it/1000);
17         
18         //3  过了多少个分钟
19         System.out.println(it/1000/60);
20         
21         //4 过了多少小时
22         System.out.println(it/1000/60/60);
23         
24         //5 过了多少天
25         System.out.println(it/1000/60/60/24);
26         
27         //6 过了多少年
28         System.out.println(it/1000/60/60/24/365);
29         
30     }
31 
32 }

方法2

 1 package com.lv.study.pm.first;
 2 
 3 import java.text.SimpleDateFormat;
 4 import java.util.Date;
 5 
 6 public class TestSimpleDateFormat {
 7 
 8     public static void main(String[] args) {
 9 
10         test2();
11         
12     }
13     
14     public static void test2(){
15         //只要符合 yyyy MM  dd HH mm  ss的规则就可以的
16         SimpleDateFormat sdf=new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
17         
18         System.out.println(sdf.format(new Date()));
19     }
20     
21     public static void test1(){
22 
23         //针对java.util.Date 做一个格式化输出
24         
25         //以指定的格式输出日期
26         SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
27         
28         //new Date()当前日期
29         String sdate=sdf.format(new Date());
30         
31         System.out.println(sdate);
32     }
33 
34 }

方法3

 1 package com.lv.study.pm.second;
 2 
 3 import java.time.LocalDate;
 4 import java.time.LocalDateTime;
 5 import java.time.LocalTime;
 6 
 7 public class TestLocalDate {
 8 
 9     public static void main(String[] args) {
10         
11         //只负责日期，不负责时间只负责年月日
12         LocalDate ld=LocalDate.now();
13         
14         System.out.println(ld.getYear());
15         System.out.println(ld.getMonth());
16         System.out.println(ld.getMonthValue());
17         System.out.println(ld.getDayOfMonth());
18         
19         //只负责时间不负责日期
20         LocalTime it=LocalTime.now();
21         System.out.println(it.getHour());
22 
23 
24         //都负责
25         LocalDateTime ldt=LocalDateTime.now();
26         System.out.println(ldt.getDayOfYear());
27         
28     }
29 }