问如何找到两个日期之间的年数？

EN

        static void diffYears1()
{
    SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MM-yyyy");
    Calendar calendar1 = Calendar.getInstance(); // now
    String toDate = dateFormat.format(calendar1.getTime());

    Calendar calendar2 = Calendar.getInstance();
    calendar2.add(Calendar.DAY_OF_YEAR, -7000); // some date in the past
    String fromDate = dateFormat.format(calendar2.getTime());

    // just simply add one year at a time to the earlier date until it becomes later then the other one 
    int years = 0;
    while(true)
    {
        calendar2.add(Calendar.YEAR, 1);
        if(calendar2.getTimeInMillis() < calendar1.getTimeInMillis())
            years++;
        else
            break;
    }

    System.out.println(years + " years between " + fromDate + " and " + toDate);
}

static void diffYears2()
{
    SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MM-yyyy");
    Calendar calendar1 = Calendar.getInstance(); // now
    String toDate = dateFormat.format(calendar1.getTime());

    Calendar calendar2 = Calendar.getInstance();
    calendar2.add(Calendar.DAY_OF_YEAR, -7000); // some date in the past
    String fromDate = dateFormat.format(calendar2.getTime());

    // first get the years difference from the dates themselves
    int years = calendar1.get(Calendar.YEAR) - calendar2.get(Calendar.YEAR);
    // now make the earlier date the same year as the later
    calendar2.set(Calendar.YEAR, calendar1.get(Calendar.YEAR));
    // and see if new date become later, if so then one year was not whole, so subtract 1 
    if(calendar2.getTimeInMillis() > calendar1.getTimeInMillis())
        years--;

    System.out.println(years + " years between " + fromDate + " and " + toDate);
}