public static Date getnewDate(Date olddate, String recordDate) throws ParseException {  Date date = olddate;  SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  String data = format.format(date);  String dataStr[] = data.split("-");  //年份  int  year = (Integer.parseInt(dataStr[1]) + Integer.parseInt(recordDate))/12;  //月份  int yue = (Integer.parseInt(dataStr[1]) + Integer.parseInt(recordDate))%12;  String a = "";  if(yue<10){    if(yue<1){      a = "12";    }else{      a = "0"+yue;    }  }else {    a = yue+"";  }  dataStr[0]=String.valueOf(Integer.parseInt(dataStr[0]) + year);  dataStr[1]=a;  String newdata = dataStr[0]+"-"+dataStr[1]+"-"+dataStr[2];  Date newDate = format.parse(newdata);  return newDate;}

package com.date.test; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date; public class Test {public static void main(String[] args) throws ParseException {SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd"); // 日期格式Date date = dateFormat.parse("2015-07-31"); // 指定日期Date newDate = addDate(date, 20); // 指定日期加上20天System.out.println(dateFormat.format(date));// 輸出格式化后的日期System.out.println(dateFormat.format(newDate));}public static Date addDate(Date date,long day) throws ParseException { long time = date.getTime(); // 得到指定日期的毫秒數 day = day*24*60*60*1000; // 要加上的天數轉換成毫秒數 time+=day; // 相加得到新的毫秒數 return new Date(time); // 將毫秒數轉換成日期} }