利用Java怎么实现计算两个日期的时间差

public static int getMonthDiff(Date d1, Date d2) {    Calendar c1 = Calendar.getInstance();    Calendar c2 = Calendar.getInstance();    c1.setTime(d1);    c2.setTime(d2);    if(c1.getTimeInMillis() < c2.getTimeInMillis()) return 0;    int year1 = c1.get(Calendar.YEAR);    int year2 = c2.get(Calendar.YEAR);    int month2 = c1.get(Calendar.MONTH);    int month3 = c2.get(Calendar.MONTH);    int day1 = c1.get(Calendar.DAY_OF_MONTH);    int day2 = c2.get(Calendar.DAY_OF_MONTH);    // 获取年的差值 假设 d1 = 2015-8-16 d2 = 2011-9-30    int yearInterval = year1 - year2;    // 如果 d1的 月-日 小于 d2的 月-日 那么 yearInterval-- 这样就得到了相差的年数    if(month2 < month3 || month2 == month3 && day1 < day2) yearInterval --;    // 获取月数差值    int monthInterval = (month2 + 12) - month3 ;    if(day1 < day2) monthInterval --;    monthInterval %= 12;    return yearInterval * 12 + monthInterval;}