New Date API介绍

一、新的Date API介绍

LocalDate
LocalTime
Instant
Duration
Period

formatter
parsejdk以前的java.util.Date存在的问题

1）比如new Date(119, 2, 18)表示Mon Mar 18 00:00:00 CST 2019，2019年3月18日，year要从1900年加起，month是从0开始，day是从1开始。

2）SimpleDateFormat不是线程安全的，比如多线程情况下simpleDateFormat.parse会出问题。

3）Date名字叫日期，但是后面还有time时间

 

例子如下：

 1 package com.cy.java8;
 2 
 3 import java.text.ParseException;
 4 import java.text.SimpleDateFormat;
 5 import java.util.Date;
 6 
 7 public class DateTest {
 8 
 9     public static void main(String[] args) throws ParseException {
10         Date date = new Date(119, 2, 18);
11         System.out.println(date);
12 
13         SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
14         for(int i=0; i<5; i++){
15             new Thread(()->{
16                 try {
17                     Date parseDate = sdf.parse("20190505");
18                     System.out.println(parseDate);
19                 } catch (ParseException e) {
20                     e.printStackTrace();
21                 }
22 
23             }).start();
24         }
25     }
26 }

 

二、LocalDate　　　　　　

 1 package com.cy.java8;
 2 
 3 import java.time.LocalDate;
 4 import java.time.temporal.ChronoField;
 5 
 6 public class DateTest {
 7 
 8     public static void main(String[] args) {
 9         testLocalDate();
10     }
11 
12     /**
13      * LocalDate是线程安全的
14      */
15     private static void testLocalDate(){
16         LocalDate localDate = LocalDate.of(2019, 10, 2);
17         System.out.println(localDate.getYear());
18         System.out.println(localDate.getMonth());
19         System.out.println(localDate.getMonthValue());
20         System.out.println(localDate.getDayOfYear());
21         System.out.println(localDate.getDayOfMonth());
22         System.out.println(localDate.getDayOfWeek());
23 
24         System.out.println(localDate.get(ChronoField.YEAR));
25         System.out.println(localDate.get(ChronoField.MONTH_OF_YEAR));
26         System.out.println(localDate.get(ChronoField.DAY_OF_MONTH));
27 
28         LocalDate now = LocalDate.now();
29         System.out.println(now);
30     }
31 }

 

console：

2019
OCTOBER
10
275
2
WEDNESDAY
2019
10
2
2019-10-02

 

三、LocalTime、Instant、Duration、Period简单介绍

 1 package com.cy.java8;
 2 
 3 import java.time.*;
 4 
 5 public class DateTest {
 6 
 7     public static void main(String[] args) throws InterruptedException {
 8         testLocalTime();
 9         System.out.println("=================================");
10 
11         testCombineLocalDateAndTime();
12         System.out.println("=================================");
13 
14         testInstant();
15         System.out.println("=================================");
16 
17         testDuration();
18         System.out.println("=================================");
19 
20         testPeriod();
21     }
22 
23     private static void testLocalTime(){
24         LocalTime time = LocalTime.now();
25         System.out.println(time);
26 
27         System.out.println(time.getHour());
28         System.out.println(time.getMinute());
29         System.out.println(time.getSecond());
30     }
31 
32     private static void testCombineLocalDateAndTime(){
33         LocalDate localDate = LocalDate.now();
34         LocalTime time = LocalTime.now();
35         LocalDateTime localDateTime = LocalDateTime.of(localDate, time);
36         System.out.println(localDateTime);
37 
38         LocalDateTime now = LocalDateTime.now();
39         System.out.println(now);
40     }
41 
42     private static void testInstant() throws InterruptedException {
43         Instant start = Instant.now();
44         Thread.sleep(1000);
45         Instant end = Instant.now();
46 
47         Duration duration = Duration.between(start, end);   //类似于之前的System.currentTimeMillis
48         System.out.println(duration.toMillis());
49     }
50 
51     private static void testDuration(){
52         LocalTime time = LocalTime.now();
53         LocalTime beforeTime = time.minusHours(1);
54         Duration duration = Duration.between(time, beforeTime);
55         System.out.println(duration.toHours());
56     }
57 
58     private static void testPeriod(){
59         Period period = Period.between(LocalDate.of(2017, 9, 1), LocalDate.of(2019, 10, 2));
60         System.out.println(period.getYears());
61         System.out.println(period.getMonths());
62         System.out.println(period.getDays());
63     }
64 }

console：

21:03:28.136
21
3
28
=================================
2019-10-02T21:03:28.137
2019-10-02T21:03:28.137
=================================
1001
=================================
-1
=================================
2
1
1

　　

四、formatter、parse

 1 package com.cy.java8;
 2 
 3 import java.time.*;
 4 import java.time.format.DateTimeFormatter;
 5 
 6 public class DateTest {
 7 
 8     public static void main(String[] args){
 9         testDateFormat();
10         System.out.println("==============================");
11 
12         testDateParse();
13     }
14 
15     private static void testDateFormat(){
16         LocalDate localDate = LocalDate.now();
17         String format1 = localDate.format(DateTimeFormatter.BASIC_ISO_DATE);
18         System.out.println(format1);
19 
20         String format2 = localDate.format(DateTimeFormatter.ISO_LOCAL_DATE);
21         System.out.println(format2);
22 
23         DateTimeFormatter myFormatter = DateTimeFormatter.ofPattern("yyyy年MM月dd日");
24         String format3 = localDate.format(myFormatter);
25         System.out.println(format3);
26     }
27 
28     private static void testDateParse(){
29         String date0 = "20191002";
30         LocalDate localDate0 = LocalDate.parse(date0, DateTimeFormatter.BASIC_ISO_DATE);
31         System.out.println(localDate0);
32 
33         String date1 = "2019-10-02";
34         LocalDate localDate1 = LocalDate.parse(date1, DateTimeFormatter.ISO_LOCAL_DATE);
35         System.out.println(localDate1);
36 
37         String date2 = "2019年10月02日";
38         LocalDate localDate2 = LocalDate.parse(date2, DateTimeFormatter.ofPattern("yyyy年MM月dd日"));
39         System.out.println(localDate2);
40     }
41 }

console：

20191002
2019-10-02
2019年10月02日
==============================
2019-10-02
2019-10-02
2019-10-02

 

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