前言
Date 类
Date 类表示系统特定的时间戳，可以精确到毫秒。Date 对象表示时间的默认顺序是星期、月、日、小时、分、秒、年。
构造方法
Date 类有如下两个构造方法。
Date()：此种形式表示分配 Date 对象并初始化此对象，以表示分配它的时间（精确到毫秒），使用该构造方法创建的对象可以获取本地的当前时间。
Date(long date)：此种形式表示从 GMT 时间（格林尼治时间）1970 年 1 月 1 日 0 时 0 分 0 秒开始经过参数 date 指定的毫秒数。
这两个构造方法的使用示例如下：
Date date1 = new Date(); // 调用无参数构造函数
System.out.println(date1.toString()); // 输出：Wed May 18 21:24:40 CST 2016
Date date2 = new Date(60000); // 调用含有一个long类型参数的构造函数
System.out.println(date2); // 输出：Thu Jan 0108:01:00 CST 1970Date 类的无参数构造方法获取的是系统当前的时间，显示的顺序为星期、月、日、小时、分、秒、年。
Date 类带 long 类型参数的构造方法获取的是距离 GMT 指定毫秒数的时间，60000 毫秒是一分钟，而 GMT（格林尼治标准时间）与 CST（中央标准时间）相差 8 小时，也就是说 1970 年 1 月 1 日 00:00:00 GMT 与 1970 年 1 月 1 日 08:00:00 CST 表示的是同一时间。 因此距离 1970 年 1 月 1 日 00:00:00 CST 一分钟的时间为 1970 年 1 月 1 日 00:01:00 CST，即使用 Date 对象表示为 Thu Jan 01 08:01:00 CST 1970。
常用方法
public final class DateUtils {
public static final SimpleDateFormat yyyyMMdd = new SimpleDateFormat("yyyyMMdd");
public static final SimpleDateFormat yyyy_MM_dd = new SimpleDateFormat("yyyy-MM-dd");
public static final SimpleDateFormat DEFAULT_FORMAT = yyyy_MM_dd;
public static final SimpleDateFormat yyyy_MM_dd_HH_mm_ss = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
public static final SimpleDateFormat yyyy_MM_dd_HH_mm_ss_SSS = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSS");
public static final SimpleDateFormat yyyy_MM_dd_HH_mm = new SimpleDateFormat("yyyy-MM-dd HH:mm");
public static final SimpleDateFormat yyyyMMddHHmmss = new SimpleDateFormat("yyyyMMddHHmmss");
public static final SimpleDateFormat yyyyMMddHHmmssSSS = new SimpleDateFormat("yyyyMMddHHmmssSSS");
public static final SimpleDateFormat yyyy_MM_ddHH_mm_ssSSS = new SimpleDateFormat("yyyy-MM-ddHH:mm:ssSSS");
public static final SimpleDateFormat MMdd = new SimpleDateFormat("MMdd");
private DateUtils() {}
public static Date parse(String date) throws ParseException{
return DEFAULT_FORMAT.parse(date);
}
public static Date parse(String date, String format) throws ParseException{
return new SimpleDateFormat(format).parse(date);
}
public static String getToday(String format) {
return new SimpleDateFormat(format).format(new Date());
}
public static String format(Date date, SimpleDateFormat format) {
if (date == null) {
return null;
}
return format.format(date);
}
public static String getToday(SimpleDateFormat format) {
return format.format(new Date());
}
public static String getToday() {
return new SimpleDateFormat("yyyy-MM-dd").format(new Date());
}
public static String getTodayMMdd() {
return MMdd.format(new Date());
}
public static int monthDifference(Calendar one, Calendar two) {
if (null == one || null == two) {
throw new NullPointerException("参数对象为空。");
}
Calendar after = one;
Calendar before = two;
if (one.before(two)) {
after = two;
before = one;
}
int deffYear = Math.abs(after.get(Calendar.YEAR) - before.get(Calendar.YEAR));
int deffMonth = after.get(Calendar.MONTH) - before.get(Calendar.MONTH);
//错误的逻辑块
return deffYear * 12 + deffMonth;
}
public static int monthDifference(Date one, Date two) {
Calendar first = new GregorianCalendar();
first.setTime(one);
Calendar second = new GregorianCalendar();
second.setTime(two);
return monthDifference(first, second);
}
public static int monthDifference(String one, String two)
throws ParseException {
Format format = new SimpleDateFormat("yyyy-MM-dd");
Date first = (java.util.Date) format.parseObject(one);
Date second = (java.util.Date) format.parseObject(two);
return monthDifference(first, second);
}
public static boolean isLastDayOfMonth(Calendar calendar) {
Calendar today = calendar;
Calendar tomorrow = (Calendar) calendar.clone();
tomorrow.add(Calendar.DAY_OF_MONTH, 1);
int todayYear = today.get(Calendar.YEAR);
int todayMonth = today.get(Calendar.MONTH) + 1;
int tomorrowYear = tomorrow.get(Calendar.YEAR);
int tomorrowMonth = tomorrow.get(Calendar.MONTH) + 1;
//是否为当月最后一天
if (tomorrowYear > todayYear || (tomorrowYear == todayYear && tomorrowMonth > todayMonth)) {
return true;
}
return false;
}
public static boolean isLastDayOfMonth(Date date) {
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
return isLastDayOfMonth(calendar);
}
public static boolean isLastDayOfMonth() {
return isLastDayOfMonth(Calendar.getInstance());
}
public static String convertMonth(int month) {
switch (month) {
case Calendar.JANUARY:
return "一月";
case Calendar.FEBRUARY:
return "二月";
case Calendar.MARCH:
return "三月";
case Calendar.APRIL:
return "四月";
case Calendar.MAY:
return "五月";
case Calendar.JUNE:
return "六月";
case Calendar.JULY:
return "七月";
case Calendar.AUGUST:
return "八月";
case Calendar.SEPTEMBER:
return "九月";
case Calendar.OCTOBER:
return "十月";
case Calendar.NOVEMBER:
return "十一月";
case Calendar.DECEMBER:
return "十二月";
default:
throw new IllegalArgumentException("表示月份的参数无效：" + month);
}
}
public static String convertDayOfWeek(int dayOfWeek) {
switch (dayOfWeek) {
case Calendar.SUNDAY:
return "周日";
case Calendar.MONDAY:
return "周一";
case Calendar.TUESDAY:
return "周二";
case Calendar.WEDNESDAY:
return "周三";
case Calendar.THURSDAY:
return "周四";
case Calendar.FRIDAY:
return "周五";
case Calendar.SATURDAY:
return "周六";
default:
throw new IllegalArgumentException("参数无效：" + dayOfWeek);
}
}
public static String convertDayOfWeek2(int dayOfWeek) {
switch (dayOfWeek) {
case Calendar.SUNDAY:
return "星期天";
case Calendar.MONDAY:
return "星期一";
case Calendar.TUESDAY:
return "星期二";
case Calendar.WEDNESDAY:
return "星期三";
case Calendar.THURSDAY:
return "星期四";
case Calendar.FRIDAY:
return "星期五";
case Calendar.SATURDAY:
return "星期六";
default:
throw new IllegalArgumentException("参数无效：" + dayOfWeek);
}
}
public static String getTodayOfWeek2() {
return convertDayOfWeek2(Calendar.getInstance().get(Calendar.DAY_OF_WEEK));
}
public static String getTodayOfWeek() {
return convertDayOfWeek(Calendar.getInstance().get(Calendar.DAY_OF_WEEK));
}
public static String getDateByMillSeconds(long millSeconds, String parseStr){
java.text.SimpleDateFormat format = new java.text.SimpleDateFormat(parseStr);
String sb=format.format(getDateByMillSeconds(millSeconds));
return sb;
}
public static Date getDateByMillSeconds(long millSeconds){
Date date = new Date(millSeconds);
GregorianCalendar gc = new GregorianCalendar();
gc.setTime(date);
return gc.getTime();
}
public static String getFirstDayByCurrentMonth(){
Calendar calendar = new GregorianCalendar();
calendar.set( Calendar.DATE, 1 );
SimpleDateFormat simpleFormate = new SimpleDateFormat( "yyyy-MM-dd" );
return simpleFormate.format(calendar.getTime());
}
public static String getLastDayByCurrentMonth(){
Calendar calendar = new GregorianCalendar();
calendar.set( Calendar.DATE, 1 );
calendar.roll(Calendar.DATE, - 1 );
SimpleDateFormat simpleFormate = new SimpleDateFormat( "yyyy-MM-dd" );
return simpleFormate.format(calendar.getTime());
}
public static Long getRealWorkminutes(Date realStartDate, Date realEndDate) throws Exception{
BigDecimal realWorkminutes = new BigDecimal("0");
long startTime = 0l;
long endTime = 0l;
long timeInterval = 0l;
if(realStartDate != null && realEndDate != null) {
startTime = realStartDate.getTime();
endTime = realEndDate.getTime();
timeInterval = endTime - startTime;
if(timeInterval > 0){
int day = (int)timeInterval/(24*60*60*1000);
int hour = (int)timeInterval/(60*60*1000)-day*24;
int min = (int)(timeInterval/(60*1000))-day*24*60-hour*60;
if(day >= 1){
realWorkminutes = new BigDecimal(day*8*60);
if(hour >= 1){
realWorkminutes = realWorkminutes.add(new BigDecimal(hour*20));
}
if(min >=1){
realWorkminutes = realWorkminutes.add(new BigDecimal(min));
}
}else{
if(hour >= 1){
realWorkminutes = realWorkminutes.add(new BigDecimal(hour*60>=480?480:hour*60));
}
if(min >=1){
realWorkminutes = realWorkminutes.add(new BigDecimal(min));
}
if(realWorkminutes.compareTo(new BigDecimal(480)) > 0) realWorkminutes = new BigDecimal(480);
}
}
}
return Long.valueOf(String.valueOf(realWorkminutes));
}
public static int getDaysBetween(String beginDate, String endDate)
throws ParseException {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
Date bDate = format.parse(beginDate);
Date eDate = format.parse(endDate);
return getDaysBetween(bDate, eDate);
}
public static int getDaysBetween(Date beginDate, Date endDate)
throws ParseException {
Calendar g1 = new GregorianCalendar();
g1.setTime(beginDate);
Calendar g2 = new GregorianCalendar();
g2.setTime(endDate);
int elapsed = 0;
GregorianCalendar gc1, gc2;
if (g2.after(g1)) {
gc2 = (GregorianCalendar) g2.clone();
gc1 = (GregorianCalendar) g1.clone();
} else {
gc2 = (GregorianCalendar) g1.clone();
gc1 = (GregorianCalendar) g2.clone();
}
gc1.clear(Calendar.MILLISECOND);
gc1.clear(Calendar.SECOND);
gc1.clear(Calendar.MINUTE);
gc1.clear(Calendar.HOUR_OF_DAY);
gc2.clear(Calendar.MILLISECOND);
gc2.clear(Calendar.SECOND);
gc2.clear(Calendar.MINUTE);
gc2.clear(Calendar.HOUR_OF_DAY);
while (gc1.before(gc2)) {
gc1.add(Calendar.DATE, 1);
elapsed++;
}
return elapsed;
}
public static long getFinalTime(long startTime, long timeInterval) {
return startTime + timeInterval;
}
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