可以从当前日期添加150天吗？

Question

我有一个像20211231这样的当前日期格式，我想在这个日期上再加150天。在那之后，如果时间还不到150天，或者已经过去了，我怎么检查呢

我尝试这个代码添加150天到当前日期，但它失败了

 Calendar c= Calendar.getInstance();
        c.add(Calendar.DATE, 150);
        Date d = c.getTime ();

idk如果它不再有效了，或者自从我读了一个9年零五个月前被问和回答的问题后又怎么样https://stackoverflow.com/a/11727986/17562398

这是我现在的约会对象

 SimpleDateFormat cdate = new SimpleDateFormat ("yyyyMMdd", Locale.getDefault ( ));
        String currentDate = cdate.format (new Date ( ));

Answer 1

这是我用currentdate（今天）检查150天的逻辑

DateFormat dateFormat = new SimpleDateFormat("yyyyMMdd");

 String sDate="20211231"; 
 Date cuDate=dateFormat.parse(sDate);  

Date currentDate = new Date();
 Calendar calendarObj = Calendar.getInstance();
        calendarObj.setTime(cuDate);

calendarObj.add(Calendar.MONTH, 5); // since this is 150 days (i think it's 30 days * 5 )

Date newDateAfter5months = calendarObj.getTime();


System.out.println("newDateAfter5months="+dateFormat.format(newDateAfter5months));


if(newDateAfter5months.compareTo(currentDate) > 0) {
         System.out.println("newDateAfter5months occurs after currentDate");
      } 

Answer 2

使用来自java.time.*包的现代JavaTime API。

可以使用java以所需格式解析或格式化（用于显示）日期。时间总体安排DateTimeFormatter。模式（字符串、区域设置）方法。以下是DateTimeFormatter类的文档

DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("yyyyMMdd", locale);

如果解析的是用户输入的日期，也不要忘记捕获解析异常。

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;

//...

// The desired locale, maybe the target user selected language/region locale?
// For now just using the default locale here
Locale locale = Locale.getDefault();
    
String someInputDate = "20220529";
    
try {
    // using the DateTimeFormatter to parse the date with a desired pattern
    DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("yyyyMMdd", locale);
    LocalDate inputDate = LocalDate.parse(someInputDate, dateFormatter);
    
    // 150 days from now
    int daysFromNow = 150;
    LocalDate targetDate = LocalDate.now().plusDays(daysFromNow);
    android.util.Log.d(
        "Dates", String.format("The date %d days from now is %s", daysFromNow, targetDate.format(dateFormatter))
    );
    if (inputDate.isAfter(targetDate)) {
        // the input date is past 150 day from now
        android.util.Log.d(
            "Dates", String.format("%s at least %d days from now", inputDate.format(dateFormatter), daysFromNow)
        );
    } else {
        // the input date is NOT past 150 day from now
        android.util.Log.d(
            "Dates", String.format("%s is less than %d days from now", inputDate.format(dateFormatter), daysFromNow)
        );    
    }
} catch (DateTimeParseException e) {
    // The input is a date in a different format or is malformed/invalid
}

日志输出

Dates    The date 150 days from now is 20220530
Dates    20220529 is less than 150 days from now