java date 時間最大連續天數

java localdate，date 時間最大連續天數

 
import java.text.SimpleDateFormat;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;
import java.util.Locale;
import java.util.Objects;
import java.util.stream.Collectors;

public class DateUtils {
  public static final String DAY_FORMAT = "yyyy-MM-dd";
  
  public static Date getDateByPattern(String time, String pattern) {
    if (time == null || time.isEmpty()) {
      return null;
    }
    try {
      SimpleDateFormat sdf = new SimpleDateFormat(pattern, Locale.ENGLISH);
      sdf.setLenient(false);
      return sdf.parse(time);
    } catch (Exception ex) {
      // log.error
      return null;
    }
  }
  
  public static Date addDays(Date time, Integer day) {
    try {
      SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
      Calendar cd = Calendar.getInstance();
      cd.setTime(time);
      cd.add(Calendar.DATE, day);
      return getDateByPattern(sdf.format(cd.getTime()), DAY_FORMAT);
    } catch (Exception ex) {
      //log.error("日期增加自然天出錯：{}", ex);
      return null;
    }
  }
  
  
  public static int continuousDayDate(List<Date> dateList) {
    if (dateList == null || dateList.isEmpty()) {
      //log.error("參數有誤,連續天數爲0  dayList{}" , dateList);
      return 0;
    }
    
    List<LocalDate> datetimeList = dateList.stream()
      .map(e -> LocalDateTime.ofInstant(e.toInstant(), ZoneId.systemDefault()).toLocalDate())
      .sorted(LocalDate::compareTo)
      .collect(Collectors.toList());
    return continuousDayLocalDate(datetimeList);
  }
  
  public static int continuousDayLocalDate(List<LocalDate> dateList) {
    if (dateList == null || dateList.size() == 0) {
      return 0;
    }
    dateList = dateList.stream().filter(Objects::nonNull).sorted(LocalDate::compareTo).collect(Collectors.toList());
    int maxContinuousDay = 1;
    int continuousDay = 1;
    
    for (int i = 1; i < dateList.size(); i++) {
      LocalDate date = dateList.get(i);
      LocalDate previousDate = dateList.get(i - 1);
      if (date.minusDays(1).equals(previousDate)) {
        continuousDay++;
        if (continuousDay > maxContinuousDay) {
          maxContinuousDay = continuousDay;
        }
      } else {
        continuousDay = 1;
      }
    }
    return maxContinuousDay;
  }
  
  public static void main(String[] args) {
    List<Date> dates = new ArrayList<>();
    Date date = new Date();
    dates.add(addDays(date, 2));
    dates.add(addDays(date, 3));
    System.out.println(continuousDayDate(dates));
    
    List<LocalDate> list = new ArrayList<>();
    list.add(LocalDate.now());
    list.add(LocalDate.now().plusDays(1));
    list.add(LocalDate.now().plusDays(2));
    System.out.println(continuousDayLocalDate(list));
  }
}