前言

最近在重构之前的一个老我的项目，其中蕴含一个统计模块，须要把存储在MongoDB的数据通过接口显示在后端管理系统中。这些数据大多是以工夫为单位进行存储，例如：collectionName_202009collectionName_20200910，在老零碎中对工夫的解决应用Date类，简略理解了其中的工夫工具类，深感繁琐并决定应用Java8中的LocalDateTime和LocalDate重构此代码。

一、根本应用

1. 获取以后工夫

        // 2020-08-23T20:14:56.977        LocalDateTime localDateTime = LocalDateTime.now();        //2020-08-23        LocalDate localDate = LocalDate.now();

1. 格式化工夫

        LocalDateTime localDateTime = LocalDateTime.now();        DateTimeFormatter localDateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss", Locale.SIMPLIFIED_CHINESE);        // 2020-08-23 20:20:29        String timeStr = localDateTime.format(localDateTimeFormatter);        LocalDate localDate = LocalDate.now();        DateTimeFormatter localDateFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");        // 2020-08-23        String dateStr = localDate.format(localDateFormatter);

1. 获取昨天、今天或者固定天数的工夫

        LocalDateTime localDateTime = LocalDateTime.now();        DateTimeFormatter localDateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss", Locale.SIMPLIFIED_CHINESE);        // 明天        String time = localDateTime.format(localDateTimeFormatter);        // 昨天        LocalDateTime yesterday = localDateTime.minusDays(1L);        String yesterdayStr = yesterday.format(localDateTimeFormatter);        // 先天        LocalDateTime tomorrow = localDateTime.plusDays(1L);        String tomorrowStr = tomorrow.format(localDateTimeFormatter);        // 天数加5        LocalDateTime timePlus = localDateTime.plusDays(5L);        String timePlusStr = timePlus.format(localDateTimeFormatter);        // 天数减5        LocalDateTime timeMinus = localDateTime.minusDays(5L);        String timeMinusStr = timeMinus.format(localDateTimeFormatter);

在LocalDateTime的API中蕴含了对各个工夫单位的减少和缩小，如：

1. 获取明天的开始工夫和完结工夫,准确到秒

        DateTimeFormatter localDateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss", Locale.SIMPLIFIED_CHINESE);        // 2020-08-23 00:00:00        String start = LocalDateTime.of(LocalDate.now(), LocalTime.MIN).format(localDateTimeFormatter);        // 2020-08-23 23:59:59        String end = LocalDateTime.of(LocalDate.now(), LocalTime.MAX).format(localDateTimeFormatter);        // 这里的LocalDate.now()示意获取明天的开始工夫和完结工夫,也能够换做任何一天

1. 获取当月的第一天和最初一天

        // 这里应用LocalDate来获取日期        DateTimeFormatter localDateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd", Locale.SIMPLIFIED_CHINESE);        LocalDate localDate = LocalDate.now();        LocalDate firstDay = localDate.with(TemporalAdjusters.firstDayOfMonth());        LocalDate lastDay = localDate.with(TemporalAdjusters.lastDayOfMonth());

1. 将工夫字符串转为工夫或日期

        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss", Locale.SIMPLIFIED_CHINESE);        String str = "2018-08-09 20:10:10";        LocalDateTime localDateTime = LocalDateTime.parse(str, formatter);        LocalDate localDate = LocalDate.parse(str, formatter);

1. 计算日期距离

        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd", Locale.SIMPLIFIED_CHINESE);        String str = "2020-09-02";        LocalDate localDate = LocalDate.parse(str, formatter);        long until = LocalDate.now().until(localDate, ChronoUnit.DAYS);

原文地址:https://www.haicheng.website/...