如何获取年-月格式的时间段？

Question

I have two strings like "March 2012" and "April 2013" . I need to subtract these dates and get something like: "1 year 2 month" .

I know how to get it in days:

df.parse(secondDate).getTime() - df.parse(firstDate).getTime())/(1000*60*60*24)

but I will receive 395 days. How can I get it in years-month format? I know it should be easy but I cannot guess how to do that.

Answer 1

For this type of problem, it is best to use the new Java Time API that was introduced in Java 8.

We have 2 Strings that represent a year and a month. Therefore, we will parse each String into a YearMonth object using a custom DateTimeFormatter . The month names are in their long English form so we will use the pattern "MMMM yyyy" .

Once they are parsed, we can get the period between those two temporal objects with Period.between . This method takes a LocalDate as parameter so we need to add a day to each YearMonth : here, we will set it to the first day of the month (what matters is that both are set to the same day).

Finally, getYears() return the amount of years in this period and getMonths() returns the amount of month.

public static void main(String[] args) {
    String startStr = "March 2012";
    String endStr = "April 2013";

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MMMM yyyy", Locale.ENGLISH);
    YearMonth start = YearMonth.parse(startStr, formatter);
    YearMonth end = YearMonth.parse(endStr, formatter);

    Period period = Period.between(start.atDay(1), end.atDay(1));

    System.out.println(period.getYears() + " years and " + period.getMonths() + " months.");
    // prints "1 years and 1 months." (you could add check for the pluralization of course ;) )
}

With this method, you don't need to worry about tricky considerations, it is handled automatically by the API.

Answer 2

Make use of the Java8 API java.time.Period , which gives you a date-based amount of time:

Period p = Period.between(firstDate, secondDate);
System.out.println(p.getYears()+" years, " + p.getMonths() + " months, and " + p.getDays() + " days.");

Answer 3

Check the below example, it should work correctly and solve leap year case as depend on year and month only:

     public static void main(String[] a) throws Exception {

    //some data initilzation for the sample
    Date d1 = new Date(), d2 = new Date();
    d1.setYear(d1.getYear() - 1); //Just for the sample, replace it with your dates
    d1.setMonth(d1.getMonth() + 5);//Just for the sample, replace it with your dates

    Calendar calendar1 = Calendar.getInstance();
    calendar1.setTime(d1);
    int year1 = calendar1.get(Calendar.YEAR);
    int month1 = calendar1.get(Calendar.MONTH) + 1;

    Calendar calendar2 = Calendar.getInstance();
    calendar2.setTime(d2);
    int year2 = calendar2.get(Calendar.YEAR);
    int month2 = calendar2.get(Calendar.MONTH) + 1;

    int yearDiff = year2 - year1;
    int monthDiff = month2 - month1;

    //Logic, in case d1  Jul 2015 and d2 Feb 2016, the need to reduce one year and put the remaining months on monthDiff value
    if (monthDiff < 0) {
        yearDiff = yearDiff - 1;
        monthDiff = monthDiff + 12;
    }

    System.out.println(" " + d1);
    System.out.println(" " + d2);

    System.out.println("yearDiff " + yearDiff + "     " + "monthsDiff " + monthDiff);

}

Answer 4

You can customize the below code as your need:

import java.util.*;
import java.lang.*;
import java.io.*;

import java.util.Calendar;
import java.text.SimpleDateFormat;

class MyClass
{
    public static void main(String[] args) throws Exception
    {
        MyClass tdt = new MyClass();
        System.out.println("Date: "+tdt.doSubtractMath("31/10/2000","31/12/2016").getTime());
    }
    /**
    * method to create a calendar object, subtract time, and return result
    */
    private Calendar doSubtractMath(String firstDate, String secondDate) throws Exception
    {
        SimpleDateFormat sdf = new SimpleDateFormat("d/MM/yyyy");

        Calendar secondDateCalender = Calendar.getInstance();

        secondDateCalender.setTime(sdf.parse(secondDate));


        Calendar firstDateCalendar = Calendar.getInstance();

        firstDateCalendar.setTime(sdf.parse(firstDate));

        secondDateCalender.add(Calendar.MINUTE, -1 * firstDateCalendar.get(Calendar.MINUTE));

        secondDateCalender.add(Calendar.HOUR, -1 * firstDateCalendar.get(Calendar.HOUR));

        secondDateCalender.add(Calendar.DAY_OF_MONTH, -1 * firstDateCalendar.get(Calendar.DAY_OF_MONTH));

        secondDateCalender.add(Calendar.YEAR, -1 * firstDateCalendar.get(Calendar.YEAR));

        return secondDateCalender;

    }
}