算法 - 常用工具类整理

• 1.将现有集合按照指定的长度拆分为几个子集合
• 2.两个时间进行比较

引入依赖包：

 
      org.apache.commons
      commons-collections4
      4.2


      com.google.guava
      guava
      23.0

 public  List> split(List resList,int subListLength) {
      if (CollectionUtils.isEmpty(resList) || subListLength <= 0) {
         return Lists.newArrayList();
      }
      int listLength = resList.size();
      List> ansList = new ArrayList<>();
      if (listLength <= subListLength) {
          ansList.add(resList);
      } else {
          int pre = listLength / subListLength;
          int last = listLength % subListLength;
          for (int i = 0; i < pre;i++) {
              ansList.add(resList.subList(subListLength * i,subListLength * (i + 1)));
          }
          if (last > 0) {
              ansList.add(resList.subList(subListLength * pre,resList.size()));
          }
      }
      return ansList;
    }

比较两个时间间间隔几天：

 // compareIntevalDays_1("2021-12-21","2021-12-22"); 打印结果为1
    public void compareIntevalDays_1(String startTime,String endTime) {
        DateTimeFormatter pattern = DateTimeFormatter.ofPattern("yyyy-MM-dd");
        LocalDate startDate = LocalDate.parse(startTime, pattern);
        LocalDate endDate = LocalDate.parse(endTime, pattern);
        Period period = Period.between(startDate, endDate);
        System.out.println(period.getDays());
    }

    // compareIntevalDays_2("2021-12-21 00:00:00","2021-12-22 01:00:00");打印结果为1。
    // 转化为LocalDate后，时分秒均为00:00:00，所以相差天数为1。但是在实际业务中如果两个时间只能间隔1天，此时这两个时间实际间隔1天1个小时，所以需要使用LocalDateTime
    public void compareIntevalDays_2(String startTime,String endTime) {
        DateTimeFormatter pattern = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        LocalDate startDate = LocalDate.parse(startTime, pattern);
        LocalDate endDate = LocalDate.parse(endTime, pattern);
        Period period = Period.between(startDate, endDate);
        System.out.println(period.getDays());
    }

    // compareIntevalDays_3("2021-12-21 00:00:00","2021-12-22 01:00:00");打印结果为1。
    public void compareIntevalDays_3(String startTime,String endTime) {
        DateTimeFormatter pattern = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        LocalDateTime startDateTime = LocalDateTime.parse(startTime, pattern);
        LocalDateTime endDateTime = LocalDateTime.parse(endTime, pattern);
        Period period = Period.between(startDateTime.toLocalDate(), endDateTime.toLocalDate()); // 这种和compareIntevalDays_2的情况一样
        System.out.println(period.getDays());
        Duration duration = Duration.between(startDateTime, endDateTime);
        long millis = duration.toMillis();//相差毫秒数
        if (millis > 24 * 60 * 60 * 1000) {
            System.out.println("开始创建时间和结束创建时间差不能超过1天"); // 控制台打印此信息
        }
    }

比较两个时间的大小：

// compareTime("2021-12-23 00:00:00","2021-12-22 01:00:00");
    public void compareTime(String startTime,String endTime) {
        DateTimeFormatter pattern = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        LocalDateTime startDateTime = LocalDateTime.parse(startTime, pattern);
        LocalDateTime endDateTime = LocalDateTime.parse(endTime, pattern);
        if (startDateTime.compareTo(endDateTime) > 0) {
            System.out.println("开始创建时间不能大于截止创建时间");// 控制台打印此信息
        }
    }