/*
* DateCalculate.java , Created on 2005-3-18
* Copyright 2005 AAA Information Technology CO.LTD. All rights reserved.
*
* 作成日期: 2005-3-18
* 修改履历:
*
*/
package com.bjb.xyh.util;
import java.text.DecimalFormat;
//import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
/**
* 类描述：自己实现的日期计算类，可以自由扩展
* @author xieyh lamp5w@yahoo.com.cn
* @version build 2005-3-18
*
*/
public class DateCalculate {
/** 注意格里历和儒略历交接时的日期差别 */
private static transient int gregorianCutoverYear = 1582;
/** 闰年中每月天数 */
private static final int[] DAYS_P_MONTH_LY=
{31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
/** 平年中每月天数 */
private static final int[] DAYS_P_MONTH_CY=
{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
/** 代表数组里的年、月、日 */
private static final int Y = 0, M = 1, D = 2;
/** 参与运算用 */
private int[] ymd = null;
/**
* 检查传入的参数是否合法的日期
* @param date
* @throws IllegalArgumentException
*/
public static void validate(String date)throws IllegalArgumentException{
int[] ymd = splitYMD( date );
if( ymd[M] == 0 || ymd[M] > 12 ){
throw new IllegalArgumentException("月份数值错误");
}
if( true == isLeapYear( ymd[0] ) ){
if( ymd[D] == 0 || ymd[D] > DAYS_P_MONTH_LY[ymd[M] -1 ] ){
throw new IllegalArgumentException("日期数值错误");
}
}else{
if( ymd[D] == 0 || ymd[D] > DAYS_P_MONTH_CY[ymd[M] -1 ] ){
throw new IllegalArgumentException("日期数值错误");
}
}
}
/**
* 检查传入的参数代表的年份是否为闰年
* @param year
* @return
*/
public static boolean isLeapYear(int year) {
return year >= gregorianCutoverYear ?
((year%4 == 0) && ((year%100 != 0) ||
(year%400 == 0))) : // Gregorian
(year%4 == 0); // Julian
}
/**
* 日期加1天，注意这里没有考虑儒略历和格里历交接时相差的10天
* @param year
* @param month
* @param day
* @return
*/
private int[] addOneDay(int year, int month, int day){
if(isLeapYear( year )){
day++;
if( day > DAYS_P_MONTH_LY[month -1 ] ){
month++;
if(month > 12){
year++;
month = 1;
}
day = 1;
}
}else{
day++;
if( day > DAYS_P_MONTH_CY[month -1 ] ){
month++;
if(month > 12){
year++;
month = 1;
}
day = 1;
}
}
int[] ymd = {year, month, day};
return ymd;
}
/**
* 以循环的方式计算日期加法
* @param date
* @param days
* @return
*/
public String addDaysByLoop(String date, int days){
validate(date);
int[] ymd = splitYMD( date );
for(int i = 0; i < days; i++){
ymd = addOneDay(ymd[Y], ymd[M], ymd[D]);
}
return formatYear(ymd[Y])+
formatMonthDay(ymd[M])+
formatMonthDay(ymd[D]);
}
/**
* 日期减1天，注意这里没有考虑儒略历和格里历交接时相差的10天
* @param year
* @param month
* @param day
* @return
*/
private int[] reduceOneDay(int year, int month, int day){
if(isLeapYear( year )){
day--;
if( day <= 0 ){
month--;
if(month < 1){
year--;
month = 12;
}
day = DAYS_P_MONTH_LY[month -1 ];
}
}else{
day--;
if( day <= 0 ){
month--;
if(month < 1){
year--;
month = 12;
}
day = DAYS_P_MONTH_CY[month -1 ];
}
}
int[] ymd = {year, month, day};
return ymd;
}
/**
* 以循环的方式计算日期减法
* @param date
* @param days
* @return
*/
public String reduceDaysByLoop(String date, int days){
validate(date);
int[] ymd = splitYMD( date );
for(int i = 0; i < days; i++){
ymd = reduceOneDay(ymd[Y], ymd[M], ymd[D]);
}
return formatYear(ymd[Y])+
formatMonthDay(ymd[M])+
formatMonthDay(ymd[D]);
}
/**
* 指定日期加上指定的天数的操作
* @param date
* @param days
* @return
* @throws IllegalArgumentException
*/
public String addDays(Date date, int days)
throws IllegalArgumentException{
return addDays(formatDate(date), days);
}
/**
* 指定日期加上指定的天数的操作
* @param date
* @param days
* @return
* @throws IllegalArgumentException
*/
public String addDays(String date, int days)
throws IllegalArgumentException{
validate(date);
ymd = splitYMD( date );
if( isLeapYear( ymd[Y] ) ){
ymd[D] += days;
if( ymd[D] > DAYS_P_MONTH_LY[ymd[M] -1 ] ){
ymd[M] ++;
ymd[D] = ymd[D] - DAYS_P_MONTH_LY[ymd[M] -1-1 ];
if(ymd[M] > 12){
ymd[M] -= 12;
ymd[Y]++;
}
if( ymd[D] > DAYS_P_MONTH_LY[ymd[M] -1 ] ){
addDays(formatYear(ymd[Y])+
formatMonthDay(ymd[M])+
formatMonthDay(DAYS_P_MONTH_LY[ymd[M] -1 ]),
ymd[D] - DAYS_P_MONTH_LY[ymd[M] -1 ]);
}
}
}else{
ymd[D] += days;
if( ymd[D] > DAYS_P_MONTH_CY[ymd[M] -1 ] ){
ymd[M] ++;
ymd[D] = ymd[D] - DAYS_P_MONTH_CY[ymd[M] -1-1 ];
if(ymd[M] > 12){
ymd[M] -= 12;
ymd[Y]++;
}
if( ymd[D] > DAYS_P_MONTH_CY[ymd[M] -1 ] ){
addDays(formatYear(ymd[Y])+
formatMonthDay(ymd[M])+
formatMonthDay(DAYS_P_MONTH_CY[ymd[M] -1 ]),
ymd[D] - DAYS_P_MONTH_CY[ymd[M] -1 ]);
}
}
}
return formatYear(ymd[Y])+
formatMonthDay(ymd[M])+
formatMonthDay(ymd[D]);
}
/**
* 指定日期减去指定的天数的操作
* @param date
* @param days
* @return
* @throws IllegalArgumentException
*/
public String reduceDays(Date date, int days)
throws IllegalArgumentException{
return reduceDays(formatDate(date), days);
}
/**
* 指定日期减去指定的天数的操作
* @param date
* @param days
* @return
* @throws IllegalArgumentException
*/
public String reduceDays(String date, int days)
throws IllegalArgumentException{
validate(date);
ymd = splitYMD( date );
if( isLeapYear( ymd[Y] ) ){
ymd[D] -= days;
if( ymd[D] <= 0 ){
ymd[M] --;
if(ymd[M] < 1){
ymd[M] += 12;
ymd[Y]--;
}
ymd[D] = ymd[D] + DAYS_P_MONTH_LY[ ymd[M]-1 ];
if( ymd[D] <= 0 ){
reduceDays(formatYear(ymd[Y])+
formatMonthDay(ymd[M])+
formatMonthDay( 1 ),
abs( ymd[D] - 1 ));
}
}
}else{
ymd[D] -= days;
if( ymd[D] <= 0 ){
ymd[M] --;
if(ymd[M] < 1){
ymd[M] += 12;
ymd[Y]--;
}
ymd[D] = ymd[D] + DAYS_P_MONTH_CY[ ymd[M]-1 ];
if( ymd[D] <= 0 ){
reduceDays(formatYear(ymd[Y])+
formatMonthDay(ymd[M])+
formatMonthDay(1),
abs( ymd[D] - 1 ));
}
}
}
return formatYear(ymd[Y])+
formatMonthDay(ymd[M])+
formatMonthDay(ymd[D]);
}
/**
* 格式化一个日期字符串
* @param date
* @return
*/
public static String formatDate(Date date){
SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
return sdf.format( date );
}
/**
* 将代表日期的字符串分割为代表年月日的整形数组
* @param date
* @return
*/
public static int[] splitYMD(String date){
int[] ymd = {0, 0, 0};
ymd[Y] = Integer.parseInt(date.substring(0, 4));
ymd[M] = Integer.parseInt(date.substring(4, 6));
ymd[D] = Integer.parseInt(date.substring(6, 8));
return ymd;
}
/**
* 将不足两位的月份或日期补足为两位
* @param decimal
* @return
*/
public static String formatMonthDay(int decimal){
DecimalFormat df = new DecimalFormat("00");
return df.format( decimal );
}
/**
* 将不足四位的年份补足为四位
* @param decimal
* @return
*/
public static String formatYear(int decimal){
DecimalFormat df = new DecimalFormat("0000");
return df.format( decimal );
}
/**
* 取绝对值操作
* @param num
* @return
*/
public static int abs(int num){
return (num > 0) ? num : -num;
}
/**
* 测试用main函数
* @param args
*/
public static void main( String[] args ) throws Exception{
String currDate = "20001231";
String currDate2 = "20001231";
int days = -36600;
Date date = null;
DateCalculate dc = new DateCalculate();
SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
date = sdf.parse( currDate2 );
System.out.println(currDate + " + " +
abs(days) + "days = " + dc.addDays(currDate, abs(days)));
System.out.println(currDate + " - " +
abs(days) + "days = " + dc.reduceDays(currDate, abs(days)));
Calendar cld = Calendar.getInstance();
cld.setTime( date );
cld.add(Calendar.DATE, abs(days));
System.out.println(currDate2 + " + " +
abs(days) + "days = " + sdf.format(cld.getTime()));
cld = Calendar.getInstance();
cld.setTime( date );
cld.add(Calendar.DATE, days);
System.out.println(currDate2 + " - " +
abs(days) + "days = " + sdf.format(cld.getTime()));
System.out.println(dc.addDaysByLoop(currDate2, abs(days)));
System.out.println(dc.reduceDaysByLoop(currDate2, abs(days)));
}
}
写这些代码的动机来自最近学习SHELL脚本的感受。
目的如下，先搁着，等有时间再作补充：
1. 避免递归算法的滥用
2. 临界值的把握
3. 日期计算的细节
