列表中的日历类型元素

Question

我必须创建一个打印日期列表（年，月，日）直到用户选择日期（end_date后来转换为end_cal）的程序。

例如，如果今天是2017-09-30 Saturday和用户输入的日期2017-10-30，程序必须打印出这些日期：

2017年9月30日，2017年10月7日，2017年10月14日，2017- 10-21，2017-10-28。

问题：

1. 添加日历类型元素融入到一个列表
2. 打印清单。另外在打印过程中
3. 格式化日期列表

当我尝试打印，输出只是一堆同日重复的。

public class Weekdays { 
    static Scanner input = new Scanner(System.in); 
    static Calendar temp_cal = Calendar.getInstance(); //temporary calendar object. it's value is being chaged in the process 
    static Calendar start_cal = Calendar.getInstance(); // current day when the program is executed 
    static Calendar end_cal = Calendar.getInstance(); //end date that the user inputs 


static SimpleDateFormat format = new SimpleDateFormat("yyyy/MM/dd"); 

public static boolean date_validation(String date){ //partial validation: whether the input date is in a correct format 
    Date test_date; 
    try { 
     test_date = format.parse(date); 

    }catch (ParseException e){ 
     return false; 
     } 
    return true; 
} 
//created list of dates that are of the same day of the week (for example all Sundays) 
static private List<Calendar> getListOfDates(){ 
    List<Calendar> dates = new ArrayList<>(); 
    while (!((temp_cal.get(Calendar.YEAR)>= end_cal.get(Calendar.YEAR))&&(temp_cal.get(Calendar.MONTH) >= end_cal.get(Calendar.MONTH))&&(temp_cal.get(Calendar.DAY_OF_YEAR) >= end_cal.get(Calendar.DAY_OF_YEAR)))) 
    { 
      temp_cal.add(Calendar.DATE, 7); 
      dates.add(temp_cal);  } 
    return dates; 
} 

static private void printListOfDates(List<Calendar> dates){ 

      System.out.println(Arrays.toString(dates.toArray())); 
} 

public static void main(String[] str) throws ParseException{ 

    String end_date = input.next(); 

    while(!(date_validation(end_date))){ 
     end_date = input.next(); 
    } 

    end_cal.setTime(format.parse(end_date));  

    printListOfDates(getListOfDates()); 

} 

输入：2018/01/01

输出（拷贝只是一个例子，整体输出是几个只是这两份）：

java.util.GregorianCalendar中[时间= 1515233525518，areFieldsSet =真，areAllFieldsSet =真，宽大=真，区= sun.util.calendar.ZoneInfo [ID = “欧洲/赫尔辛基”，偏移= 7200000，dstSavings = 3600000，useDaylight =真，过渡= 118，lastRule = java.util.SimpleTimeZone中[ID =欧洲/赫尔辛基，偏移= 7200000，dstSavings = 3600000，useDaylight =真，startYear = 0，STARTMODE = 2，startMonth = 2，开始天= -1，startDayOfWeek = 1，开始时间= 3600000，startTimeMode = 2，endMode = 2，endMonth = 9，endday指定= -1，一个endDayOfWeek = 1，结束时间= 3600000，endTimeMode = 2]]，Firstdayofweek可= 2，minimalDaysInFirstWeek = 4，ERA = 1，YEAR = 2018，MONTH = 0，WEEK_OF_YEAR = 1，WEEK_OF_MONTH = 1，DAY_OF_MONTH = 6，DAY_OF_YEAR = 6，DAY_OF_WEEK = 7，DAY_OF_WEEK_IN_MONTH = 1，AM_PM = 1，HOUR = 0，HOUR_OF_DAY = 12，分= 12，秒= 5，多段微差= 518，ZONE_OFFSET = 7200000，DST_OFFSET = 0]]

Answer 1

第一个问题是你打印出结果的方式：

System.out.println(Arrays.toString(dates.toArray())); 

如果你想格式化的日期，您将需要使用格式化程序。

private static SimpleDateFormat outputFormat = new SimpleDateFormat("yyyy-MM-dd"); 

static private void printListOfDates(List<Calendar> dates){ 
    for (Calendar date : dates) { 
     System.out.println(outputFormat.format(date)); 
    } 
} 

第二个问题是，您似乎在getListOfDates的循环中重复使用了相同的temp_cal对象。这会导致您的列表包含同一个Calendar对象的多个副本（多次修改）。您需要为循环中的每个迭代创建一个新实例。

Answer 2

我不知道，如果这是你的正确的格式（我将离开这个作为你一个任务），但你可以用做这样的事情LocalDate：

import java.util.Scanner; 
import java.time.LocalDate; 
import java.time.format.DateTimeFormatter; 

class Main { 
    public static void main(String[] args) { 
    Scanner scanner = new Scanner(System.in); 

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy/MM/dd"); 
    LocalDate endDate; 

    while(true){ 
     System.out.print("Enter the endDate in the format of yyyy/MM/dd:"); 
     String date = scanner.next(); 
     try { 
     endDate = LocalDate.parse(date, formatter); 
     break; 
     } catch (Exception e) { 
     System.err.println("ERROR: Please input the date in the correct format"); 
     } 
    } 

    System.out.println("Below are the days between the current day and " + endDate); 
    printDaysBetween(endDate); 
    } 

    public static void printDaysBetween(LocalDate end){ 
    LocalDate start = LocalDate.now(); 
    while (!start.isAfter(end)) { 
     System.out.println(start); 
     start = start.plusDays(7); 
    } 
    } 
} 

使用示例：

Enter the endDate in the format of yyyy/MM/dd: 2017-10-30 
ERROR: Please input the date in the correct format 
Enter the endDate in the format of yyyy/MM/dd: 2017/10/30 
Below are the days between the current day and 2017-10-30 
2017-09-30 
2017-10-07 
2017-10-14 
2017-10-21 
2017-10-28 

Answer 3

import java.util.Date; 
import java.time.*; 
import java.text.SimpleDateFormat; 
import java.util.*; 
public class days 
{ 
public static void main (String args[]){ 
    Scanner input = new Scanner(System.in); 
    System.out.println("Enter Dates (Start(yyyy/mm/dd)-End)"); 
    //example 2017 1 5 -> 5 jan 2017 
    getDates(Integer.parseInt(input.next()),Integer.parseInt(input.next()), 
       Integer.parseInt(input.next()),Integer.parseInt(input.next()), 
        Integer.parseInt(input.next()),Integer.parseInt(input.next())); 
    /*the input needed example 
    * 2017 
    * 1 
    * 1  -Start date 
    * 2017 
    * 2 
    * 10  -End date 
    */ 

} 

public static void getDates(int pYearStart, int pMonthStart, int pDayStart, 
            int pYearEnd, int pMonthEnd, int pDayEnd){ 
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy MMM dd"); 
    int year = pYearStart; 
    int month = pMonthStart-1; 
    int day = pDayStart; 
    Calendar start = new GregorianCalendar(year,month,day); 
    int yearEnd = pYearEnd; 
    int monthEnd = pMonthEnd-1; 
    int dayEnd = pDayEnd; 
    Calendar end = new GregorianCalendar(yearEnd,monthEnd,dayEnd); 
    System.out.print("Start Date: "); 
    System.out.println(sdf.format(start.getTime())); 

    System.out.print("End Date: "); 
    System.out.println(sdf.format(end.getTime())); 

    System.out.println(""); 
    System.out.println("All Dates:"); 

    boolean sameDate = false; 
    int amount = 0; 
    do{ 

     System.out.println(sdf.format(start.getTime())); 
     start.add(Calendar.DAY_OF_MONTH, 7); 
     amount++; 
     if(start.get(Calendar.DAY_OF_MONTH) >= end.get(Calendar.DAY_OF_MONTH) && 
     start.get(Calendar.MONTH) == end.get(Calendar.MONTH)) { 
      sameDate = true;} 
    }while(sameDate != true); 
    System.out.println("No of dates: "+amount); 
    } 
} 

我觉得这是你想要的，我没有使用一个列表，但瓒什么只要你喜欢就可以。