Here you can find the source of dateAddDays(Date date, int days)
public static Date dateAddDays(Date date, int days)
//package com.java2s; //License from project: Apache License import java.util.*; public class Main { private static long DAY_IN_MILLISECOND = 0x5265c00L; public static Date dateAddDays(Date date, int days) { long now = date.getTime() + (long) days * DAY_IN_MILLISECOND; return new Date(now); }/*from w w w . j ava 2s . c o m*/ }