//日期转字符串,根据需要调整格式

@Testpublic voidDateToString(){

Date currentTime= newDate();

SimpleDateFormat formatter= new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

String dateString=formatter.format(currentTime);

System.out.println(dateString);

}字符串转日期

void StrToDate() throwsParseException {

String dateStr= "2019-01-19";

SimpleDateFormat format= new SimpleDateFormat("yyyy-MM-dd");

Date date= null;

date=format.parse(dateStr);

System.out.println(date);

}获取本月第一天

void getMonthFirstDay() ParseException {

SimpleDateFormat format= );

Calendar cal=Calendar.getInstance();获取当前日期

cal.set(Calendar.DAY_OF_MONTH,1);设置为1号,当前日期既为本月第一天

String monthFirstDay =format.format(cal.getTime());

System.out.println(monthFirstDay);

}获取本月最后一天

void getMonthLastDay() 获取当前日期

cal.set(Calendar.DAY_OF_MONTH,cal.getActualMaximum(Calendar.DAY_OF_MONTH));

String monthLastDay=format.format(cal.getTime());

System.out.println(monthLastDay);

}获取上个月第一天。最后一天同理

void getLastMonthFirstDay() 获取当前日期

cal.add(Calendar.MONTH,-1);

cal.set(Calendar.DAY_OF_MONTH,1);通过Calendar获取年月日时分秒

void testCalendar() ParseException {

Calendar cal=Calendar.getInstance();赋值时年月日时分秒常用的6个值，注意月份下标从0开始，所以取月份要+1

System.out.println("年:" +cal.get(Calendar.YEAR));

System.out.println("月:" + (cal.get(Calendar.MONTH) + 1));

System.out.println("日:" +cal.get(Calendar.DAY_OF_MONTH));

System.out.println("时:" +cal.get(Calendar.HOUR_OF_DAY));

System.out.println("分:" +cal.get(Calendar.MINUTE));

System.out.println("秒:" +cal.get(Calendar.SECOND));

}得到两个时间相隔的天数

void getBetweenDay() ParseException{

String dateStr1= "2019-01-01";

String dateStr2= "2019-01-19";

SimpleDateFormat format= );

Date date1=format.parse(dateStr1);

Date date2=format.parse(dateStr2);

Long inteverDay= (date2.getTime()-date1.getTime())/(1000*60*60*24);

System.out.println(inteverDay);

}当前日期加一天

void addCurrentDay() ParseException {

String datess= "2019-02-28");

Date parse=format.parse(datess);

Calendar cal=Calendar.getInstance();cal.setTime(parse);

cal.add(Calendar.DAY_OF_YEAR,+1);

String monthFirstDay=Calendar转换成date

void CalToDate() ParseException {

Calendar cal=Calendar.getInstance();

Date date=cal.getTime();

}date转换成Calendar

void DateToCal() Calendar.getInstance();

Date date= Date();

cal.setTime(date);

}获得当前周周一的日期

getMonday(){

Date date= Date();

Calendar c=Calendar.getInstance();

c.setTime(date);monday可以替换成任意星期几

c.set(Calendar.DAY_OF_WEEK,Calendar.MONDAY);

String dateStr= ).format(c.getTime());

System.out.println(dateStr);

}判断两个时间是否在同一周

booleanisSameWeekDates(Date date1,Date date2) {

Calendar cal1=Calendar.getInstance();

Calendar cal2=Calendar.getInstance();

cal1.setTime(date1);

cal2.setTime(date2);int subYear = cal1.get(Calendar.YEAR) -cal2.get(Calendar.YEAR);if (0 ==subYear) {if (cal1.get(Calendar.WEEK_OF_YEAR) ==cal2.get(Calendar.WEEK_OF_YEAR)){return true;

}

}else if (1 == subYear && 11 ==cal2.get(Calendar.MONTH)) {如果12月的最后一周横跨来年第一周的话则最后一周即算做来年的第一周

if (-1 == subYear && 11 ==cal1.get(Calendar.MONTH)) {;

}

}false;

}