Here you can find the source of addDate(Date date, int day)
public static Date addDate(Date date, int day)
//package com.java2s; //License from project: Apache License import java.text.DateFormat; import java.text.SimpleDateFormat; import java.util.Calendar; import java.util.Date; public class Main { public static Date addDate(Date date, int day) { Calendar calendar = Calendar.getInstance(); long millis = getMillis(date) + day * 24L * 3600L * 1000L; calendar.setTimeInMillis(millis); return calendar.getTime(); }//from w ww . j ava2s .c om public static long getMillis(Date date) { Calendar calendar = Calendar.getInstance(); calendar.setTime(date); return calendar.getTimeInMillis(); } public static String getTime(Date date) { return format(date, "HH:mm:ss"); } public static String format(Date date, String format) { String result = ""; try { if (date != null) { DateFormat dateFormat = new SimpleDateFormat(format); result = dateFormat.format(date); } } catch (Exception localException) { } return result; } public static String format(Date date) { return format(date, "yyyy-MM-dd"); } }