2021-10-19

2021-10-19 记录一些码农经常用到的小方法

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记性不好，写下来，以后还会慢慢补充

文章目录

• 记录一些码农经常用到的小方法
• 一、java部分
• 1. 日期处理工具
• 2. 集合去重
• 2. 格式化小数位
• 3. list的使用
• 4. stream流的使用

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提示：以下是本篇文章正文内容，下面案例可供参考

一、java部分 1. 日期处理工具

public class DateUtils extends PropertyEditorSupport {
    
    public final static String DATE_PATTERN = "yyyy-MM-dd";
    
    public final static String PATTERN = "yyyyMMdd";
    
    public final static String DATE_TIME_PATTERN = "yyyy-MM-dd HH:mm:ss";

    
    public static String getDate(String pattern) {
        return DateFormatUtils.format(new Date(), pattern);
    }

    
    public static String format(Date date) {
        return format(date, DATE_PATTERN);
    }

    
    public static String format(Date date, String pattern) {
        if (date != null) {
            SimpleDateFormat df = new SimpleDateFormat(pattern);
            return df.format(date);
        }
        return null;
    }

    
    public static Date stringToDate(String strDate, String pattern) {
        if (StringUtils.isBlank(strDate)) {
            return null;
        }

        DateTimeFormatter fmt = DateTimeFormat.forPattern(pattern);
        return fmt.parseLocalDateTime(strDate).toDate();
    }

    
    public static Date[] getWeekStartAndEnd(int week) {
        DateTime dateTime = new DateTime();
        LocalDate date = new LocalDate(dateTime.plusWeeks(week));

        date = date.dayOfWeek().withMinimumValue();
        Date beginDate = date.toDate();
        Date endDate = date.plusDays(6).toDate();
        return new Date[]{beginDate, endDate};
    }

    //根据年份和当年的第几周，获取这一周的日期
    public static String getDayOfWeek(int year, int weekindex) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Calendar c = Calendar.getInstance();
        c.setWeekDate(year, weekindex, 1);

        int dayOfWeek = c.get(Calendar.DAY_OF_WEEK) - 2;
        c.add(Calendar.DATE, -dayOfWeek); // 得到本周的第一天
        String begin = sdf.format(c.getTime());
        c.add(Calendar.DATE, 6); // 得到本周的最后一天
        String end = sdf.format(c.getTime());
        String range = begin + "," + end;
        return range;
    }

    
    public static int getWeekNumByTime(String start, String end){
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        try {
            long from = df.parse(start).getTime();
            long to = df.parse(end).getTime();
            int num = (int) ((to-from)/(1000*3600*24*7));
            return num;
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return 0;
    }

    
    public static Date addDateSeconds(Date date, int seconds) {
        DateTime dateTime = new DateTime(date);
        return dateTime.plusSeconds(seconds).toDate();
    }

    
    public static Date addDateMinutes(Date date, int minutes) {
        DateTime dateTime = new DateTime(date);
        return dateTime.plusMinutes(minutes).toDate();
    }

    
    public static Date addDateHours(Date date, int hours) {
        DateTime dateTime = new DateTime(date);
        return dateTime.plusHours(hours).toDate();
    }

    
    public static Date addDateDays(Date date, int days) {
        DateTime dateTime = new DateTime(date);
        return dateTime.plusDays(days).toDate();
    }

    
    public static Date addDateWeeks(Date date, int weeks) {
        DateTime dateTime = new DateTime(date);
        return dateTime.plusWeeks(weeks).toDate();
    }

    
    public static Date addDateMonths(Date date, int months) {
        DateTime dateTime = new DateTime(date);
        return dateTime.plusMonths(months).toDate();
    }

    
    public static Date addDateYears(Date date, int years) {
        DateTime dateTime = new DateTime(date);
        return dateTime.plusYears(years).toDate();
    }

    
    public static String getBeforeByHourTime(int ihour) {
        String returnstr = "";
        Calendar calendar = Calendar.getInstance();
        calendar.set(Calendar.HOUR_OF_DAY, calendar.get(Calendar.HOUR_OF_DAY) - ihour);
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        returnstr = df.format(calendar.getTime());
        return returnstr;
    }

    // 获取当前时间和hour小时前的时间
    public static Map dealTime(int hour) {
        Calendar calendar = Calendar.getInstance();
        Calendar calendar2 = Calendar.getInstance();
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        SimpleDateFormat simpleDateFormat2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        calendar2.add(Calendar.MINUTE, 1); //往前1分钟
        String etime = simpleDateFormat2.format(calendar2.getTime());
        int a = Calendar.HOUR_OF_DAY;
        calendar.set(Calendar.HOUR_OF_DAY, calendar.get((Calendar.HOUR_OF_DAY)) - hour);
        String stime = simpleDateFormat.format(calendar.getTime());
        Map map = new HashMap();
        map.put("stime", stime);
        map.put("etime", etime);
        return map;
    }

    
    public static List getDatesBetweenTwoDate(String beginDate, String endDate)
            throws ParseException, java.text.ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        List lDate = new ArrayList();
        Date date = null;
        try {
            date = new SimpleDateFormat("yyyy-MM-dd").parse(beginDate);
        } catch (java.text.ParseException e) {
            e.printStackTrace();
        }
        String dateString = sdf.format(date);
        lDate.add(dateString);
        Calendar cal = Calendar.getInstance();
        cal.setTime(sdf.parse(beginDate));
        boolean bContinue = true;
        while (bContinue) {
            cal.add(Calendar.DAY_OF_MONTH, 1);
            if (sdf.parse(endDate).after(cal.getTime())) {
                lDate.add(sdf.format(cal.getTime()));
            } else {
                break;
            }
        }

        try {
            date = new SimpleDateFormat("yyyy-MM-dd").parse(beginDate);
        } catch (java.text.ParseException e) {
            e.printStackTrace();
        }
        String entrs = sdf.format(date);
        if (!dateString.equals(entrs)) {
            lDate.add(entrs);
        }
        return lDate;
    }

    //返回两个时间段之间的所有月包含最后一个月
    public static List getMonthBetweenTwoDateIncludeEndDate(String beginDate, String endDate)
            throws ParseException, java.text.ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM");
        List lDate = new ArrayList();
        Date date = null;
        try {
            date = new SimpleDateFormat("yyyy-MM").parse(beginDate);
        } catch (java.text.ParseException e) {
            e.printStackTrace();
        }
        String dateString = sdf.format(date);
        lDate.add(dateString);
        Calendar cal = Calendar.getInstance();
        cal.setTime(sdf.parse(beginDate));
        boolean bContinue = true;
        while (bContinue) {
            cal.add(Calendar.MONTH, 1);
            if (sdf.parse(endDate).after(cal.getTime())) {
                lDate.add(sdf.format(cal.getTime()));
            } else {
                break;
            }
        }

        try {
            date = new SimpleDateFormat("yyyy-MM").parse(endDate);
        } catch (java.text.ParseException e) {
            e.printStackTrace();
        }
        String entrs = sdf.format(date);
        if (!dateString.equals(entrs)) {
            lDate.add(entrs);
        }
        return lDate;
    }

    //返回两个时间段之间的所有日期包含最后一天
    public static List getDatesBetweenTwoDateIncludeEndDate(String beginDate, String endDate)
            throws ParseException, java.text.ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        List lDate = new ArrayList();
        Date date = null;
        try {
            date = new SimpleDateFormat("yyyy-MM-dd").parse(beginDate);
        } catch (java.text.ParseException e) {
            e.printStackTrace();
        }
        String dateString = sdf.format(date);
        lDate.add(dateString);
        Calendar cal = Calendar.getInstance();
        cal.setTime(sdf.parse(beginDate));
        boolean bContinue = true;
        while (bContinue) {
            cal.add(Calendar.DAY_OF_MONTH, 1);
            if (sdf.parse(endDate).after(cal.getTime())) {
                lDate.add(sdf.format(cal.getTime()));
            } else {
                break;
            }
        }

        try {
            date = new SimpleDateFormat("yyyy-MM-dd").parse(endDate);
        } catch (java.text.ParseException e) {
            e.printStackTrace();
        }
        String entrs = sdf.format(date);
        if (!dateString.equals(entrs)) {
            lDate.add(entrs);
        }
        return lDate;
    }

    
    public static List getHoursBetweenTwoDate(String beginDate, String endDate)
            throws ParseException, java.text.ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH");
        List lDate = new ArrayList();
        Date date = null;
        try {
            date = new SimpleDateFormat("yyyy-MM-dd HH:mm").parse(beginDate);
        } catch (java.text.ParseException e) {
            e.printStackTrace();
        }
        String dateString = sdf.format(date);
        lDate.add(dateString);
        Calendar cal = Calendar.getInstance();
        cal.setTime(sdf.parse(beginDate));
        boolean bContinue = true;
        while (bContinue) {
            cal.add(Calendar.HOUR, 1);
            if (sdf.parse(endDate).after(cal.getTime())) {
                lDate.add(sdf.format(cal.getTime()));
            } else {
                break;
            }
        }

        try {
            date = new SimpleDateFormat("yyyy-MM-dd HH:mm").parse(endDate);
        } catch (java.text.ParseException e) {
            e.printStackTrace();
        }
        String endstr = sdf.format(date);
        lDate.add(endstr);
        return lDate;
    }

    
    public static List getMinuteBetweenTwoDate(String beginDate, String endDate)
            throws ParseException, java.text.ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm");
        List lDate = new ArrayList();
        lDate.add(beginDate);// 把开始时间加入集合
        Calendar cal = Calendar.getInstance();
        // 使用给定的 Date 设置此 Calendar 的时间
        cal.setTime(sdf.parse(beginDate));
        boolean bContinue = true;
        while (bContinue) {
            // 根据日历的规则，为给定的日历字段添加或减去指定的时间量
            cal.add(Calendar.MINUTE, 1);
            // 测试此日期是否在指定日期之后
            if (sdf.parse(endDate).after(cal.getTime())) {
                lDate.add(sdf.format(cal.getTime()));
            } else {
                break;
            }
        }
        lDate.add(endDate);// 把结束时间加入集合
        return lDate;
    }

    public static List getMinuteBetweenTwoDate(String beginDate, String endDate,Integer min)
            throws ParseException, java.text.ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm");
        List lDate = new ArrayList();
        // 判定beginData 是否是5的倍数
        Date dt = sdf.parse(beginDate);
        int minute = dt.getMinutes();
        minute = minute % min;
        beginDate = DateUtils.formatDate(DateUtils.getRightDate(dt, -minute+min),"yyyy-MM-dd HH:mm");
        lDate.add(beginDate);// 把开始时间加入集合
        Calendar cal = Calendar.getInstance();
        // 使用给定的 Date 设置此 Calendar 的时间
        cal.setTime(sdf.parse(beginDate));
        boolean bContinue = true;
        while (bContinue) {
            // 根据日历的规则，为给定的日历字段添加或减去指定的时间量
            cal.add(Calendar.MINUTE, min);

            // 测试此日期是否在指定日期之后
            if (sdf.parse(endDate).after(cal.getTime())) {
                lDate.add(sdf.format(cal.getTime()));
            } else {
                break;
            }
        }
        lDate.add(endDate);// 把结束时间加入集合
        return lDate;
    }


    
    public static List getMinutes(String day) throws ParseException, java.text.ParseException {
        List minuteList = getMinuteBetweenTwoDate(day + " 00:00", day + " 23:59");
        return minuteList;
    }

    
    public static String getSecond(int i) {
        long l = Math.round(Math.random() * i);
        if (l < 10) {
            return "0" + l;
        } else {
            if (l != i) {
                return "" + l;
            } else {
                return l - 1 + "";
            }
        }
    }

    
    public static String getRandom(int i) {
        double d = Math.random() * i;
        return String.format("%.2f", d);
    }

    //获取两个时间之间的分钟数
    public static int getMinNums(String stime, String etime) {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Date now = null;
        Date date = null;
        try {
            now = df.parse(etime);
            date = df.parse(stime);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        long l = now.getTime() - date.getTime();
        int day = (int) l / (24 * 60 * 60 * 1000);
        int hour = (int) (l / (60 * 60 * 1000));
        int min = (int) ((l / (60 * 1000)));
        int s = (int) (l / 1000);
//		System.out.println(""+day+"天"+hour+"小时"+min+"分"+s+"秒");
        return min;
    }

    //获取两个时间之间的小时数
    public static int getHourNums(String stime, String etime) {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Date now = null;
        Date date = null;
        try {
            now = df.parse(etime);
            date = df.parse(stime);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        long l = now.getTime() - date.getTime();
        int day = (int) l / (24 * 60 * 60 * 1000);
        int hour = (int) (l / (60 * 60 * 1000));
        int min = (int) ((l / (60 * 1000)));
        int s = (int) (l / 1000);
//		System.out.println(""+day+"天"+hour+"小时"+min+"分"+s+"秒");
        return hour;
    }

    //获取两个时间之间的天数
    public static int getDayNums(String stime, String etime) {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Date now = null;
        Date date = null;
        try {
            now = df.parse(etime);
            date = df.parse(stime);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        long l = now.getTime() - date.getTime();
        int day = (int) l / (24 * 60 * 60 * 1000);
        int hour = (int) (l / (60 * 60 * 1000));
        int min = (int) ((l / (60 * 1000)));
        int s = (int) (l / 1000);
//		System.out.println(""+day+"天"+hour+"小时"+min+"分"+s+"秒");
        return day;
    }

    
    public static List getDatesBetweenT(String beginDate, String endDate, String simpleFormat)
            throws ParseException, java.text.ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat(simpleFormat);
        List lDate = new ArrayList();
        Date date = null;
        try {
            date = new SimpleDateFormat(simpleFormat).parse(beginDate);
        } catch (java.text.ParseException e) {
            e.printStackTrace();
        }
        String dateString = sdf.format(date);
        lDate.add(dateString);
        Calendar cal = Calendar.getInstance();
        cal.setTime(sdf.parse(beginDate));
        boolean bContinue = true;
        while (bContinue) {
            cal.add(Calendar.DAY_OF_MONTH, 1);
            if (sdf.parse(endDate).after(cal.getTime())) {
                lDate.add(sdf.format(cal.getTime()));
            } else {
                break;
            }
        }

        try {
            date = new SimpleDateFormat(simpleFormat).parse(beginDate);
        } catch (java.text.ParseException e) {
            e.printStackTrace();
        }
        String entrs = sdf.format(date);
        if (!dateString.equals(entrs)) {
            lDate.add(entrs);
        }
        return lDate;
    }

    
    public static List getMonthBetween(String minDate, String maxDate) throws ParseException {
        ArrayList result = new ArrayList();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM");

        Calendar min = Calendar.getInstance();
        Calendar max = Calendar.getInstance();

        min.setTime(sdf.parse(minDate));
        min.set(min.get(Calendar.YEAR), min.get(Calendar.MONTH), 1);

        max.setTime(sdf.parse(maxDate));
        max.set(max.get(Calendar.YEAR), max.get(Calendar.MONTH), 2);

        Calendar curr = min;
        while (curr.before(max)) {
            result.add(sdf.format(curr.getTime()));
            curr.add(Calendar.MONTH, 1);
        }

        return result;
    }

    
    public static int daysOfTwo_2(String stime, String etime) throws ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        
        Date fDate = sdf.parse(stime);
        Date oDate = sdf.parse(etime);
        Long a = ((oDate.getTime() - fDate.getTime()) / (1000 * 3600 * 24));
        int days = a.intValue();
        return days;
    }

    
    public static String getNowDate() {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        return df.format(new Date());
    }

    
    public static int getDaysOfMonth(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        return calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
    }

    
    public static Date getCurrYearFirst(int year) {
        Calendar calendar = Calendar.getInstance();
        calendar.clear();
        calendar.set(Calendar.YEAR, year);
        Date currYearFirst = calendar.getTime();
        return currYearFirst;
    }

    
    public static Date getCurrYearLast(int year) {
        Calendar calendar = Calendar.getInstance();
        calendar.clear();
        calendar.set(Calendar.YEAR, year);
        calendar.roll(Calendar.DAY_OF_YEAR, -1);
        Date currYearLast = calendar.getTime();

        return currYearLast;
    }

    
    public static int getRightMinute(Date date) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        return c.get(Calendar.MINUTE);
    }

    
    public static Date getRightDate(Date date, int minute) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        c.add(Calendar.MINUTE, minute);
        return c.getTime();
    }

    
    public static String getYear() {
        return formatDate(new Date(), "yyyy");
    }

    
    public static String formatDate(Date date, Object... pattern) {
        String formatDate = null;
        if (pattern != null && pattern.length > 0) {
            formatDate = DateFormatUtils.format(date, pattern[0].toString());
        } else {
            formatDate = DateFormatUtils.format(date, "yyyy-MM-dd");
        }
        return formatDate;
    }

    
    public static String getMonth() {
        return formatDate(new Date(), "MM");
    }


    
    public static String getDay() {
        return formatDate(new Date(), "dd");
    }

    
    public static Map getYearToMonthStartEnd(String dateStr){
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Calendar c = Calendar.getInstance();
        Calendar c1 = Calendar.getInstance();
        try {
            c.setTime(sdf.parse(dateStr));
            c.add(Calendar.MONTH, 0);
            //设置为1号,当前日期既为本月第一天
            c.set(Calendar.DAY_OF_MONTH, 1);
            c1.setTime(sdf.parse(dateStr));
            c1.set(Calendar.DAY_OF_MONTH, c.getActualMaximum(Calendar.DAY_OF_MONTH));
            c1.set(Calendar.HOUR_OF_DAY, 23);
            c1.set(Calendar.MINUTE, 59);
            c1.set(Calendar.SECOND, 59);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        Map map = new HashMap<>();
        map.put("stime",DateUtils.formatDate(c.getTime(),"yyyy-MM-dd HH:mm:ss"));
        map.put("etime",DateUtils.formatDate(c1.getTime(),"yyyy-MM-dd HH:mm:ss"));
        return map;
    }
}

2. 集合去重

//方法1
public List> removeDuplicate(List> list) {
        for (int i = 0; i < list.size() - 1; i++) {
            for (int j = list.size() - 1; j > i; j--) {
                if (list.get(j).get("monitorName").equals(list.get(i).get("monitorName")) && list.get(j).get("pointName").equals(list.get(i).get("pointName"))) {
                    list.remove(j);
                }
            }
        }
        return list;
}
//方法2
public static List removeDuplicate(List list) {   
    HashSet h = new HashSet(list);   
    list.clear();   
    list.addAll(h);   
    return list;   
} 

2. 格式化小数位

    public static String formatNum(Float value,Integer n) {
        NumberFormat nf = NumberFormat.getNumberInstance();
        nf.setMaximumFractionDigits(n);
        nf.setRoundingMode(RoundingMode.HALF_UP);
        nf.setGroupingUsed(false);
        String num = nf.format(value);
        return num;
    }

    
    public static String formatNum(Double value,Integer n) {
        NumberFormat nf = NumberFormat.getNumberInstance();
        nf.setMaximumFractionDigits(n);
        nf.setRoundingMode(RoundingMode.HALF_UP);
        nf.setGroupingUsed(false);
        String num = nf.format(value);
        return num;
    }

3. list的使用

//根据条件出去空值
list.removeIf(p->(p.getPointCode() == null));

//List是你需要换位置的List。  i是你当前需要换位置的元素的索引    j是你需要将这个元素换到哪个索引
Collections.swap(List,i,j)

//根据amount降序排序
Collections.sort(returnList, Comparator.comparing(ExportExhaustDataPO::getAmount).reversed());
//给List

4. stream流的使用

//对集合按照单个属性分组
Map> detailsMap01 = dtos1.stream()
.collect(Collectors.groupingBy(EntryDeliveryDetailywk::getskuId));

//对集合按照多个属性分组			
Map> detailmap = details.stream()
.collect(Collectors.groupingBy(d -> fetchGroupKey(d) ));

private String fetchGroupKey(EntryDeliveryDetailywk detail){
        return detail.getSkuId().toString() 
        + detail.getItemsName() 
        + detail.getWarehouseId().toString()   
        + detail.getSupplierId().toString();
}

//stream流去重用（可以根据属性去重
list = list.stream().filter(distinctByKey(b -> b.getName()))
              .forEach(b -> System.out.println(b.getName()+ "," + b.getPrice()));
              
private static  Predicate distinctByKey(Function keyExtractor) {
        Map seen = new ConcurrentHashMap<>();
        return t -> seen.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) == null;
}

list.stream().mapToDouble(User::getHeight).sum()//和
list.stream().mapToDouble(User::getHeight).max()//最大
list.stream().mapToDouble(User::getHeight).min()//最小
list.stream().mapToDouble(User::getHeight).average()//平均值

//获取actualQuaulity值最大的对象
TrenchMapPointNewestEntity maxPoint = valueList.stream().filter(c->c.getActualQuaulity() != null).max(Comparator.comparing(TrenchMapPointNewestEntity::getActualQuaulity)).get();

//list 转 Map集合
public Map listToMapWithDupKey(List books) {
    return books.stream().collect(Collectors.toMap(Book::getReleaseYear,Function.identity(),
      (existing, replacement) -> existing));
}

//list 转 TreeMap集合
public TreeMap listToSortedMap(List books) {
    return books.stream() 
      .sorted(Comparator.comparing(Book::getName))
      .collect(Collectors.toMap(Book::getName, Function.identity(), (o1, o2) -> o1, TreeMap::new));
}

//list 转 ConcurrentHashMap集合
public Map listToConcurrentMap(List books) {
    return books.stream().collect(Collectors.toMap(Book::getReleaseYear, Function.identity(),
      (o1, o2) -> o1, ConcurrentHashMap::new));
}

//拼接字符串
String unitorwayStr = monthList.stream().map(str->{return str.getUnitorway();}).filter(str-> str != null && !"".equals(str)).distinct().collect(Collectors.joining("，"));