Java8 日期时间操作

作者: xiaogp | 来源:发表于2020-07-17 14:21 被阅读0次

操作包括

java.util.Date().getTime()返回13位时间戳

System.currentTimeMillis 计算毫秒差

SimpleDateFormat 解析和格式化日期

LocalDate

LocalTime

LocalDateTime

Duration

Period

计算日间隔 toEpochDay

日期相互加减

日期时间和日期相互转换

时间类型和时间戳互相转化

java.util.Date().getTime()

返回13位时间戳

        long a = new java.util.Date().getTime();
        System.out.println(a);  // 1602243261784

System.currentTimeMillis

常用来计时, 单位是毫秒

// 使用 System.currentTimeMillis
    // 主要用来计算时间差
    public static void getDiffTime() {
        try {
            long start = System.currentTimeMillis();
            Thread.sleep(1000);
            long end = System.currentTimeMillis();
            System.out.println(end - start);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

SimpleDateFormat

常用来解析和格式化日期

// SimpleDateFormat 常用来输出标准格式日期
    // yyyy-MM-dd HH:mm:ss
    public static void getFormatDate() {
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
        System.out.println(simpleDateFormat.format(new Date()));
    }

    public static void getParseDate() {
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
        try {
            Date date = simpleDateFormat.parse("2020-02-02");
            System.out.println(date);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

LocalDate

获得日期类型的时间, 并且获得年月日

// LocalDate 获得当前日期, 并且获得年. 月, 日
    public static void getNowDate() {
        LocalDate date = LocalDate.now();
        System.out.println(date);
        System.out.println(date.getDayOfMonth());
        System.out.println(date.getMonthValue());
        System.out.println(date.getYear());

        // 可以format
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy");
        String formatDate = date.format(formatter);
        System.out.println(formatDate);
    }

LocalTime

获得当前的日期时间, 并且获得时,分,秒

// LocalTime, 获得当前的日期时间, 并且获得时,分,秒
    public static void getNowTime() {
        LocalTime time = LocalTime.now();  // 20:13:56.241
        System.out.println(time);
        System.out.println(time.getHour());
        System.out.println(time.getMinute());
        System.out.println(time.getSecond());

        // 可以format
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("HH:mm:ss");
        String formatTime = time.format(formatter);
        System.out.println(formatTime);
    }

LocalDateTime

获得当前的日期时间, 并且获得年月日时分秒

// LocalDateTime, 获得当前的日期时间, 并且获得年月日时分秒
    public static void getNowDateTime() {
        LocalDateTime datetime = LocalDateTime.now();
        System.out.println(datetime);
        System.out.println(datetime.getYear());
        System.out.println(datetime.getDayOfMonth());
        System.out.println(datetime.getMonthValue());
        System.out.println(datetime.getHour());
        System.out.println(datetime.getMinute());
        System.out.println(datetime.getSecond());

        // format
        DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        String formatDatetime = datetime.format(dateTimeFormatter);
        System.out.println(formatDatetime);  // 2020-07-17 09:22:54
    }

获得指定时间类型的数据

可以使用parse解析输入的字符串

// 指定日期时间
    public static void getTimeDefine() {
        String time1 = "2020-02-02";
        String time2 = "2020-02-02 15:03";
        String time3 = "16:20:20";
        LocalDate time1Parse = LocalDate.parse(time1);
        System.out.println(time1Parse);
        System.out.println(time1Parse.getDayOfMonth());

        LocalDateTime time2Parse = LocalDateTime.parse(time2, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm"));
        System.out.println(time2Parse);
        System.out.println(time2Parse.getHour());
        System.out.println(time2Parse.getSecond());  // 默认是0
        // 解析之后再格式化输出
        System.out.println(time2Parse.format(DateTimeFormatter.ofPattern("yyyy:MM:dd HH:mm:ss")));

        LocalTime time3Parse = LocalTime.parse(time3);
        System.out.println(time3Parse);
        System.out.println(time3Parse.getHour());
        System.out.println(time3Parse.format(DateTimeFormatter.ofPattern("HH:mm")));
    }

或者使用of方法

public static void getTimeDefine2() {
        LocalDateTime time1 = LocalDateTime.of(2020, 2, 3, 13, 2, 33);
        System.out.println(time1);
        System.out.println(time1.getYear());
        System.out.println(time1.getSecond());

        LocalDate time2 = LocalDate.of(2020, 2, 3);
        System.out.println(time2);
        System.out.println(time2.getDayOfMonth());
        System.out.println(time2.getYear());
    }

Duration

时间区间, 使用秒和纳秒衡量, 只能用DateTime

// 计算日期差
    public static void getDiffDate() {
        // Duration用秒和纳秒衡量时间, 所以只能用LocalDateTime
        LocalDateTime date1 = LocalDateTime.parse("2020-02-02 00:00:00", DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
        LocalDateTime date2 = LocalDateTime.of(2020, 4, 2, 0, 0, 0);
        Duration duration = Duration.between(date1, date2);
        System.out.println(duration.toString());  // PT-744H
        System.out.println(duration.toDays());  // 后 - 前
        System.out.println(duration.toHours());
        System.out.println(duration.toMillis());
    }

Period

时间区间, 衡量年月日和几天之间的时间值

// 计算日期差Period
    public static void getDiddDate2() {
        // Period
        // 计算间隔多少年月天, 以大单位先开始排, toTotalMonths可以获得总共间隔多少月
        LocalDate date1 = LocalDate.of(2018, 2, 2);
        LocalDate date2 = LocalDate.of(2020, 1, 10);
        Period period = Period.between(date1, date2);
        System.out.println(period.getYears());
        System.out.println(period.getDays());
        System.out.println(period.getMonths());
        System.out.println(period.toTotalMonths());
        System.out.printf("区间间隔%d年%d月%d天\n", period.getYears(), period.getMonths(), period.getDays());
    }

toEpochDay 计算相差多少日

// 计算日期相差多少天
    public static void getDiffDay() {
        LocalDate date1 = LocalDate.of(2020, 2, 3);
        LocalDate date2 = LocalDate.of(2020, 1, 19);
        long date1EpochDay = date1.toEpochDay();  // 返回的是距离1970-01-01的天数
        System.out.println(date1EpochDay);
        long diffDays = date1.toEpochDay() - date2.toEpochDay();
        System.out.println(diffDays);
    }

日期相加减

// 日期相加减
    public static void plusMinDay() {
        LocalDate date1 = LocalDate.of(2020, 2, 3);
        LocalDate date2 = date1.plusDays(3);
        System.out.println(date2);
        LocalDate date3 = date1.plusYears(2);
        System.out.println(date3);
        LocalDate date4 = date1.minusDays(10);
        System.out.println(date4);
        LocalDate date5 = date1.minusDays(-10);
        System.out.println(date5);
    }

时间, 日期, 日期时间之间的互相转化

// time, date, datetime之间互相转化
    public static void dateToTimeStamp() {
        // date => datetime    asTime
        LocalDate date1 = LocalDate.of(2020, 1, 2);
        LocalDateTime time1 = date1.atTime(LocalTime.parse("06:30:20"));
        LocalDateTime time2 = date1.atTime(LocalTime.of(6,30,30));
        System.out.println(time1.toString());
        System.out.println(time2.toString());

        // time => datetime
        LocalTime time6 = LocalTime.of(13, 13, 13);
        LocalDateTime date3 = time6.atDate(LocalDate.parse("2020-02-02"));
        System.out.println(date3);

        // datetime => date / time
        LocalDateTime time3 = LocalDateTime.of(2020, 2, 2, 13, 1, 1);
        LocalDate date2 = time3.toLocalDate();
        System.out.println(date2.toString());
        LocalTime time4 = time3.toLocalTime();
        System.out.println(time4);
    }

时间类型和时间戳互相转化

// 转化为时间戳
    public static void dateTimeToTimestamp() {
        // datetime转时间戳
        LocalDateTime time1 = LocalDateTime.of(2020,2,2,2,2,2);
        long timestrap = time1.atZone(ZoneId.systemDefault()).toInstant().toEpochMilli();
        System.out.println(timestrap);  // 1580580122000   13位时间戳

        // 时间戳转datetime
        Instant instant = Instant.ofEpochMilli(1580580122000L);
        LocalDateTime time2 = LocalDateTime.ofInstant(instant, ZoneId.systemDefault());
        System.out.println(time2.toString());

    }

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