Java8中的LocalDateTime和Date一些时间操作

本是古典何须时尚 2022-01-31 16:34 355阅读 0赞

先记录下jdk8之前的一些帮助方法

**判断time是否在now的n天之内**

/**
         * 判断time是否在now的n天之内
         * @param time
         * @param now
         * @param n    正数表示在条件时间n天之后，负数表示在条件时间n天之前
         * @return
         */
        public static boolean belongDate(Date time, Date now, int n) {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            Calendar calendar = Calendar.getInstance();  //得到日历
            calendar.setTime(now);//把当前时间赋给日历
            calendar.add(Calendar.DAY_OF_MONTH, n);
            Date before7days = calendar.getTime();   //得到n前的时间
            if (before7days.getTime() < time.getTime()) {
                return true;
            } else {
                return false;
            }
        }

**判断某个时间是否是在条件的起始时间与结束时间之内**

/**
         * 判断time是否在from，to之内
         *
         * @param time 指定日期
         * @param from 开始日期
         * @param to   结束日期
         * @return
         */
        public static boolean belongCalendar(Date time, Date from, Date to) {
            Calendar date = Calendar.getInstance();
            date.setTime(time);
     
            Calendar after = Calendar.getInstance();
            after.setTime(from);
     
            Calendar before = Calendar.getInstance();
            before.setTime(to);
     
            if (date.after(after) && date.before(before)) {
                return true;
            } else {
                return false;
            }
        }

**判断给定时间与当前时间相差多少天**

public static long getDistanceDays(String date) {
            DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
            long days = 0;
            try {
                Date time = df.parse(date);//String转Date
                Date now = new Date();//获取当前时间
                long time1 = time.getTime();
                long time2 = now.getTime();
                long diff = time1 - time2;
                days = diff / (1000 * 60 * 60 * 24);
            } catch (Exception e) {
                e.printStackTrace();
            }
            return days;//正数表示在当前时间之后，负数表示在当前时间之前
        }

**将Date转换成String**

private static final String LONG_PATTERN="yyyy-MM-dd HH:mm:ss";
        private static final String SHORT_PATTERN="yyyy-MM-dd";
    
        /**
         * 将日期转换为字符串
         */
        public static String parse( Date d, String pattern){
            DateFormat df=null;
            if( pattern!=null && !"".equals(pattern) ){
                df=new SimpleDateFormat(pattern);
            }else{
                df=new SimpleDateFormat(LONG_PATTERN);
            }
            return df.format( d );
        }

**将String转换成Date**

private static final String LONG_PATTERN="yyyy-MM-dd HH:mm:ss";
     private static final String SHORT_PATTERN="yyyy-MM-dd";
    
    /**
         * 将字符串转为日期
         */
        public static Date parseStringToDate(String str, String pattern){
            DateFormat df = null;
            if( pattern!=null && !"".equals(pattern) ){
                df=new SimpleDateFormat( pattern );
            }else{
                df=new SimpleDateFormat( LONG_PATTERN );
            }
            Date d=null;
            try {
                d=df.parse(str);
            } catch (ParseException e) {
                e.printStackTrace();
            }
            return d;
    
        }

**获取指定年后的日期(例如三年后的日期)**

Calendar date = Calendar.getInstance();
            date.setTime(new Date());
            date.add(Calendar.YEAR, +3);
            //倒计时结束后的时间
            Date scrap_year = date.getTime();
            System.out.println("三年后时间" + scrap_year);

**Jdk8改革**

**LocalDateTime获取毫秒数**

//获取秒数
    Long second = LocalDateTime.now().toEpochSecond(ZoneOffset.of("+8"));
    //获取毫秒数
    Long milliSecond = LocalDateTime.now().toInstant(ZoneOffset.of("+8")).toEpochMilli();

## LocalDateTime与String互转 ##

//时间转字符串格式化
     DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS");
     String dateTime = LocalDateTime.now(ZoneOffset.of("+8")).format(formatter);
     
    //字符串转时间
    String dateTimeStr = "2018-07-28 14:11:15";
    DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    LocalDateTime dateTime = LocalDateTime.parse(dateTimeStr, df);

## Date与LocalDateTime互转 ##

//将java.util.Date 转换为java8 的java.time.LocalDateTime,默认时区为东8区
        public static LocalDateTime dateConvertToLocalDateTime(Date date) {
            return date.toInstant().atOffset(ZoneOffset.of("+8")).toLocalDateTime();
        }
     
       
        //将java8 的 java.time.LocalDateTime 转换为 java.util.Date，默认时区为东8区
        public static Date localDateTimeConvertToDate(LocalDateTime localDateTime) {
            return Date.from(localDateTime.toInstant(ZoneOffset.of("+8")));
        }

**将LocalDateTime转为自定义的时间格式的字符串**

public static String getDateTimeAsString(LocalDateTime localDateTime, String format) {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern(format);
        return localDateTime.format(formatter);
    }

**将某时间字符串转为自定义时间格式的LocalDateTime**

public static LocalDateTime parseStringToDateTime(String time, String format) {
        DateTimeFormatter df = DateTimeFormatter.ofPattern(format);
        return LocalDateTime.parse(time, df);
    }

**将long类型的timestamp转为LocalDateTime**

public static LocalDateTime getDateTimeOfTimestamp(long timestamp) {
        Instant instant = Instant.ofEpochMilli(timestamp);
        ZoneId zone = ZoneId.systemDefault();
        return LocalDateTime.ofInstant(instant, zone);
    }

**将LocalDateTime转为long类型的timestamp**

public static long getTimestampOfDateTime(LocalDateTime localDateTime) {
        ZoneId zone = ZoneId.systemDefault();
        Instant instant = localDateTime.atZone(zone).toInstant();
        return instant.toEpochMilli();
    }