LocalDate笔记

╰+攻爆jí腚メ 2023-02-15 12:56 19阅读 0赞

## 来源 ##

占小狼发布的一篇博客

## Date ##

Java处理日期、日历和时间的不足之处：将 java.util.Date 设定为可变类型，以及 SimpleDateFormat 的非线程安全使其应用非常受限。然后就在 java8 上面增加新的特性。

## LocalDate ##

1.  Instant 瞬时实例。
2.  LocalDate：本地日期，不包含具体时间 例如：2014-01-14 可以用来记录生日、纪念日、加盟日等。
3.  LocalTime：本地时间，不包含日期。
4.  LocalDateTime：组合了日期和时间，但不包含时差和时区信息。
5.  ZonedDateTime：最完整的日期时间，包含时区和相对UTC或格林威治的时差。

新API还引入了 ZoneOffSet 和 ZoneId 类，使得解决时区问题更为简便。解析、格式化时间的 DateTimeFormatter 类也全部重新设计。

package com.test;
    
    import java.time.*;
    import java.time.format.DateTimeFormatter;
    import java.time.temporal.ChronoUnit;
    import java.util.Date;
    /** * @author xxx * @date 2020/6/5 16:43 * @desc ... copy */
    public class T { 
    
        //DATE --> LocalDate
        public static LocalDate date2LocalDate(Date date) { 
            return date.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
        }
        
       // LocalDate --> DATE
        public static Date localDate2Date(LocalDate localDate) { 
            if(null == localDate) { 
                return null;
            }
            ZonedDateTime zonedDateTime = localDate.atStartOfDay(ZoneId.systemDefault());
            return Date.from(zonedDateTime.toInstant());
        }
        
        // localDateTime --> DATE
        public static Date localDateTime2Date(LocalDateTime localDateTime) { 
            return Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant());
        }
    
        //DATE --> String
        public static String formatDate(Date date) { 
            LocalDate localDate = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
            return localDate.format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));
        }
    
    //LocalDateTime 转 Long
    localDateTime.atZone(ZoneId.systemDefault()).toInstant().toEpochMilli())
    //Long转 LocalDateTime 
    LocalDateTime.ofInstant(Instant.ofEpochMilli(timestamp), ZoneId.systemDefault()).toLocalDate());
    
    
        //获取今天的日期
        public void getCurrentDate(){ 
            LocalDate today = LocalDate.now();
            System.out.println("Today's Local date : " + today);
        }
    
        //获取年、月、日信息
        public void getDetailDate(){ 
            LocalDate today = LocalDate.now();
            int year = today.getYear();
            int month = today.getMonthValue();
            int day = today.getDayOfMonth();
            System.out.printf("Year : %d Month : %d day : %d t %n", year, month, day);
        }
    
        //处理特定日期
        public void handleSpecilDate(){ 
            LocalDate dateOfBirth = LocalDate.of(2018, 01, 21);
            System.out.println("The specil date is : " + dateOfBirth);
        }
    
    
        //获取当前时间
        public void getCurrentTime(){ 
            LocalTime time = LocalTime.now();
            System.out.println("local time now : " + time);
        }
    
        // LocalTime 加减时间
        public void plusHours(){ 
            LocalTime time = LocalTime.now();
            LocalTime newTime = time.plusHours(2); // 增加两小时
            System.out.println("Time after 2 hours : " +  newTime);
            LocalTime time1 = time.minusHours(2);  //减少两小时
            System.out.println("Time after 2 hours : " +  time1);
    
        }
    
        //LocalDate 加减时间
        public void nextWeek(){ 
            LocalDate today = LocalDate.now();
            //加一周
            LocalDate nextWeek = today.plus(1, ChronoUnit.WEEKS);
    		//减一个月
            LocalDate nextWeek = today.minus(1, ChronoUnit.DAYS;
            
            System.out.println("Today is : " + today);
            System.out.println("Date after 1 week : " + nextWeek);
        }
    
    
    
        public void clock(){ 
            // 根据系统时间返回当前时间并设置为UTC。
            Clock clock = Clock.systemUTC();
            System.out.println("Clock : " + clock);
    
            // 根据系统时钟区域返回时间
            Clock defaultClock = Clock.systemDefaultZone();
            System.out.println("Clock : " + clock);
        }
    
    
        //时区处理
        public void getZoneTime(){ 
            //设置时区
            ZoneId america = ZoneId.of("America/New_York");
    
            LocalDateTime localtDateAndTime = LocalDateTime.now();
    
            ZonedDateTime dateAndTimeInNewYork  = ZonedDateTime.of(localtDateAndTime, america );
            System.out.println("现在的日期和时间在特定的时区 : " + dateAndTimeInNewYork);
        }
    
        //检查闰年
        public void isLeapYear(){ 
            LocalDate today = LocalDate.now();
            if(today.isLeapYear()){ 
                System.out.println("This year is Leap year");
            }else { 
                System.out.println("2018 is not a Leap year");
            }
        }
    
        //计算两个日期之间的天数和月数
        public void calcDateDays(){ 
            LocalDate today = LocalDate.now();
    
            LocalDate java8Release = LocalDate.of(2018, Month.MAY, 14);
    
            Period periodToNextJavaRelease = Period.between(today, java8Release);
    
            System.out.println("Months left between today and Java 8 release : "
                    + periodToNextJavaRelease.getMonths() );
        }
    
        // 包含时差信息的日期和时间
        public void ZoneOffset(){ 
            LocalDateTime datetime = LocalDateTime.of(2018, Month.FEBRUARY, 14, 19, 30);
            ZoneOffset offset = ZoneOffset.of("+05:30");
            OffsetDateTime date = OffsetDateTime.of(datetime, offset);
            System.out.println("Date and Time with timezone offset in Java : " + date);
        }
    
        // 获取时间戳
        public void getTimestamp(){ 
            Instant timestamp = Instant.now();
            System.out.println("What is value of this instant " + timestamp);
        }
    
        // 使用预定义的格式化工具去解析或格式化日期
        public void formateDate(){ 
            String dayAfterTommorrow = "20180210";
            LocalDate formatted = LocalDate.parse(dayAfterTommorrow, DateTimeFormatter.BASIC_ISO_DATE);
            System.out.printf("Date generated from String %s is %s %n", dayAfterTommorrow, formatted);
        }
    }

获取当月第一天

LocalDate first= LocalDate.now().with(TemporalAdjusters.firstDayOfMonth());

获取当月最后一天

LocalDate with = LocalDate.now().with(TemporalAdjusters.lastDayOfMonth());

获取某天0点0分0秒 ->Long（LocalDate，LocalDateTime）

//Long
     LocalDate date1 = LocalDate.now();
     long s= date1.atStartOfDay(ZoneId.systemDefault()).toInstant().toEpochMilli() 
     //LocalDate
     LocalDate.now().atStartOfDay(ZoneId.systemDefault()).toLocalDate();
     //LocalDateTime 
     LocalDateTime qws = LocalDateTime.of(LocalDate.now(), LocalTime.MIN);

获取某天23点59分59秒 ->Long（LocalDate，LocalDateTime）

LocalDateTime dsdf = LocalDateTime.of(LocalDate.now(), LocalTime.MAX);

String yyyy-MM 转 LocalDate

DateTimeFormatter fmt = DateTimeFormatter.ofPattern("yyyy-MM");
      YearMonth ym = YearMonth.parse("2020-09", fmt);
      LocalDate date = ym.atEndOfMonth();//月末
      LocalDate date1 = ym.atDay(0);//月初

LocalDate 转 String yyyy-MM

DateTimeFormatter DATE_DTF = DateTimeFormatter.ofPattern("yyyy-MM");
      String statisticDate = LocalDate.now().format(DATE_DTF);