想要得到只是天(没有时间)，你可以使用ChronoUnit

ChronoUnit.DAYS.between(date1.toLocalDate(), date2.toLocalDate());

下面的方法非常适合我:

public int daysBetween(LocalDate later, LocalDate before) {
        SimpleDateFormat myFormat = new SimpleDateFormat("dd MM yyyy");
        int daysBetween = 0;
        try {
            Date dateBefore = myFormat.parse(localDateToString(before));
            Date dateAfter = myFormat.parse(localDateToString(later));
            long difference = dateAfter.getTime() - dateBefore.getTime();
            daysBetween = (int) (difference / (1000 * 60 * 60 * 24));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return daysBetween;
    }

    public String localDateToString(LocalDate date) {
        DateTimeFormatter myFormat = DateTimeFormatter.ofPattern("dd MM yyyy");
        return date.format(myFormat).toString();
    }

最好的方法，它转换为一个字符串作为奖励;)

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    try {
        //Dates to compare
        String CurrentDate=  "09/24/2015";
        String FinalDate=  "09/26/2015";

        Date date1;
        Date date2;

        SimpleDateFormat dates = new SimpleDateFormat("MM/dd/yyyy");

        //Setting dates
        date1 = dates.parse(CurrentDate);
        date2 = dates.parse(FinalDate);

        //Comparing dates
        long difference = Math.abs(date1.getTime() - date2.getTime());
        long differenceDates = difference / (24 * 60 * 60 * 1000);

        //Convert long to String
        String dayDifference = Long.toString(differenceDates);

        Log.e("HERE","HERE: " + dayDifference);
    }
    catch (Exception exception) {
        Log.e("DIDN'T WORK", "exception " + exception);
    }
}

更新:2013年的原始答案现在已经过时，因为一些类已经被替换了。新的方法是使用新的java。时间类。

DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd MM yyyy");
String inputString1 = "23 01 1997";
String inputString2 = "27 04 1997";

try {
    LocalDateTime date1 = LocalDate.parse(inputString1, dtf);
    LocalDateTime date2 = LocalDate.parse(inputString2, dtf);
    long daysBetween = Duration.between(date1, date2).toDays();
    System.out.println ("Days: " + daysBetween);
} catch (ParseException e) {
    e.printStackTrace();
}

注意，这个解决方案给出的是实际的24小时天数，而不是日历天数。对于后者，请使用

long daysBetween = ChronoUnit.DAYS.between(date1, date2)

原始答案(Java 8已过时)

您正在使用字符串进行一些不必要的转换。有一个SimpleDateFormat类-试试这个:

SimpleDateFormat myFormat = new SimpleDateFormat("dd MM yyyy");
String inputString1 = "23 01 1997";
String inputString2 = "27 04 1997";

try {
    Date date1 = myFormat.parse(inputString1);
    Date date2 = myFormat.parse(inputString2);
    long diff = date2.getTime() - date1.getTime();
    System.out.println ("Days: " + TimeUnit.DAYS.convert(diff, TimeUnit.MILLISECONDS));
} catch (ParseException e) {
    e.printStackTrace();
}

编辑:由于有一些关于这段代码正确性的讨论:它确实考虑到了闰年。然而，TimeUnit.DAYS.convert函数失去了精度，因为毫秒被转换为天(更多信息请参阅链接文档)。如果这是一个问题，diff也可以手动转换:

float days = (diff / (1000*60*60*24));

注意，这是一个浮点值，不一定是整型。

public static String dateCalculation(String getTime, String dependTime) {
    //Time A is getTime that need to calculate.
    //Time B is static time that Time A depend on B Time and calculate the result.

    Date date = new Date();
    final SimpleDateFormat sdf = new SimpleDateFormat("yyy-MM-dd H:mm:ss");
    Date dateObj = null;
    Date checkDate = null;

    try {
        dateObj = sdf.parse(getTime);
    } catch (ParseException e) {
        e.printStackTrace();
        return "0";
    }
    SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");

    String checkInDate = dateFormat.format(dateObj).toString();
    Date defaultTime = null;
    try {
        defaultTime = dateFormat.parse(dependTime);
        checkDate = dateFormat.parse(checkInDate);
    } catch (ParseException e) {
        e.printStackTrace();
        return "0";
    }

    try {
        if (dateFormat.parse(dateFormat.format(date)).after(defaultTime)) {
            long diff = checkDate.getTime() - defaultTime.getTime();
            Log.e("Difference", "onBindViewHolder: Difference: " + dateObj + " : " + defaultTime + " : " + diff);
            if (diff > 0) {
                long diffSeconds = diff / 1000 % 60;
                long diffMinutes = diff / (60 * 1000) % 60;
                long diffHours = diff / (60 * 60 * 1000);

                return "Late: " + diffHours + " Hour, " + diffMinutes + " Minutes, " + diffSeconds + " Sec";
            } else {
                return "0";
            }
        }
    } catch (ParseException e) {
        e.printStackTrace();
        return "0";
    }
    return "0";
}

public class TestCode {

    public static void main(String[] args) {        
        String date1 = "23-04-2021";
        String date2 = "24-05-2021";
        System.out.println("NDays: " + nDays_Between_Dates(date1, date2));      
    }
    
    public static int nDays_Between_Dates(String date1, String date2) {
        int diffDays = 0;
        try {
            SimpleDateFormat dates = new SimpleDateFormat("dd-MM-yyyy");
            Date startDate = dates.parse(date1);
            Date endDate = dates.parse(date2);
            long diff = endDate.getTime() - startDate.getTime();
            diffDays = (int) (diff / (24 * 60 * 60 * 1000));            
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return Math.abs(diffDays);
    }
}

nday: 31天