[Java] 计算两个日期之间的差(年 月 日)

在项目中有这样的需求：   需要显示剩余的年月日。如下表：

起始时间                截至期                     有效期 

              2011-01-01          2013-12-31            3年

2011-01-01          2011-01-01            1天

代码如下： 主要是参考 remainDateToString（）方法

/**
 * 处理平台的时间转换
 * @author alf
 * 2011-8-31 上午09:21:39
 */
public class DateHandler {
    private static Calendar calS=Calendar.getInstance();
    private static Pattern   p   =   Pattern.compile("\\d{4}-\\d{2}-\\d{2}");//定义整则表达式
    private DateHandler(){}
    /**
     * 计算剩余时间
     * @param startDateStr
     * @param endDateStr
     * @return
     */
    public static String remainDateToString(String startDateStr, String endDateStr){
        java.util.Date startDate = null;
        java.util.Date endDate= null;
        try {
            startDate = new SimpleDateFormat("yyyy-MM-dd").parse(startDateStr);
        } catch (ParseException e) {
            e.printStackTrace();
            return "";
        }
        try {
            endDate = new SimpleDateFormat("yyyy-MM-dd").parse(endDateStr);
        } catch (ParseException e) {
            e.printStackTrace();
            return "";
        }
        calS.setTime(startDate);
        int startY = calS.get(Calendar.YEAR);
        int startM = calS.get(Calendar.MONTH);
        int startD = calS.get(Calendar.DATE);
        int startDayOfMonth = calS.getActualMaximum(Calendar.DAY_OF_MONTH);

        calS.setTime(endDate);
        int endY = calS.get(Calendar.YEAR);
        int endM = calS.get(Calendar.MONTH);
        //处理2011-01-10到2011-01-10，认为服务为一天
        int endD = calS.get(Calendar.DATE)+1;
        int endDayOfMonth = calS.getActualMaximum(Calendar.DAY_OF_MONTH);

        StringBuilder sBuilder = new StringBuilder();
        if (endDate.compareTo(startDate)<0) {
            return sBuilder.append("过期").toString();
        }
        int lday = endD-startD;
        if (lday<0) {
            endM = endM -1;
            lday = startDayOfMonth+ lday;
        }
        //处理天数问题，如：2011-01-01 到 2013-12-31  2年11个月31天     实际上就是3年
        if (lday == endDayOfMonth) {
            endM = endM+1;
            lday =0;
        }
        int mos = (endY - startY)*12 + (endM- startM);
        int lyear = mos/12;
        int lmonth = mos%12;
        if (lyear >0) {
            sBuilder.append(lyear+"年");
        }
        if (lmonth > 0) {
            sBuilder.append(lmonth+"个月");
        }
        if (lday >0 ) {
            sBuilder.append(lday+"天");
        }
        return sBuilder.toString();
    }

    /*
     * 转换 dataAndTime 2013-12-31 23:59:59 到
     * date 2013-12-31
     */
    public static String getDate(String dateAndTime){
        if (dateAndTime != null && !"".equals(dateAndTime.trim())) {
            Matcher   m   =  p.matcher(dateAndTime);
            if (m.find()) {
                  return dateAndTime.subSequence(m.start(), m.end()).toString();
            }
        }
        return "data error";
    }

    public static void main(String[] args) {
        System.out.println(remainDateToString("2004-02-29", "2005-04-01"));
        System.out.println("A");
        Date time1=new Date();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
        String tm=sdf.format(time1);//tm就是昨天的日期的字符串表示
        System.out.println(tm);
    }
}