小结: 这里是利用 Calendar 日历类进行设置
1.1 获取当前时间所在月的第一天
private static Date getFirstDayDateOfMonth(final Date date) {
final Calendar cal = Calendar.getInstance();
cal.setTime(date);
final int last = cal.getActualMinimum(Calendar.DAY_OF_MONTH);
cal.set(Calendar.DAY_OF_MONTH, last);
Date time = cal.getTime();
return processFirstDate(time);
}
private static Date processFirstDate(Date time) {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String firstDate = df.format(time);
StringBuilder firstDateTimeStr = new StringBuilder().append(firstDate).append(" 00:00:00");
Date firstDateTime = null;
try {
firstDateTime = sdf.parse(firstDateTimeStr.toString());
} catch (ParseException e) {
e.printStackTrace();
}
return firstDateTime;
}
测试结果:
@Test
private void testFirstDayOfMonth(){
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
// 获取当前时间
long currentTimeMillis = System.currentTimeMillis();
Date currentDate = new Date(currentTimeMillis);
// 获取当前时间所在月的第一天
Date firstDayDateOfMonth = getFirstDayDateOfMonth(currentDate);
System.out.println("当前时间为:"+format.format(currentTimeMillis));
System.out.println("当前时间为:"+format.format(firstDayDateOfMonth));
}
}
private Date getCurrentDate() {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
long currentTimeMillis = System.currentTimeMillis();
Date currentDate = new Date(currentTimeMillis);
System.out.println("当前时间为:" + format.format(currentDate));
return currentDate;
}
// 输出结果
//当前时间为:2021-09-28 09:12:03
//所在月第一天为:2021-09-01 00:00:00
1.2 获取当前时间所在月的最后一天
private static Date getLastDayOfMonth(final Date date) {
final Calendar cal = Calendar.getInstance();
cal.setTime(date);
final int last = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
cal.set(Calendar.DAY_OF_MONTH, last);
Date time = cal.getTime();
return processDate(time);
}
private static Date processDate(Date time) {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String lastDate = df.format(time);
StringBuilder lastDateTimeStr = new StringBuilder().append(lastDate).append(" 23:59:59");
Date lastDateTime = null;
try {
lastDateTime = sdf.parse(lastDateTimeStr.toString());
} catch (ParseException e) {
e.printStackTrace();
}
return lastDateTime;
}
测试结果:
@Test
void testLastDayOfMonth() {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
// 获取当前时间
Date currentDate = getCurrentDate();
// 获取当前时间所在月的最后一天
Date lastDayOfMonth = getLastDayOfMonth(currentDate);
System.out.println("所在月第一天为:" + format.format(lastDayOfMonth));
}
private Date getCurrentDate() {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
long currentTimeMillis = System.currentTimeMillis();
Date currentDate = new Date(currentTimeMillis);
System.out.println("当前时间为:" + format.format(currentDate));
return currentDate;
}
// 运行结果
//当前时间为:2021-09-28 09:17:38
//所在月第一天为:2021-09-30 23:59:59
1.3 获取当前时间所在年的第一天
public static Date getFirstDayDateOfYear(final Date date) {
final Calendar cal = Calendar.getInstance();
cal.setTime(date);
final int last = cal.getActualMinimum(Calendar.DAY_OF_YEAR);
cal.set(Calendar.DAY_OF_YEAR, last);
Date time = cal.getTime();
return processFirstDate(time);
}
private static Date processFirstDate(Date time) {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String firstDate = df.format(time);
StringBuilder firstDateTimeStr = new StringBuilder().append(firstDate).append(" 00:00:00");
Date firstDateTime = null;
try {
firstDateTime = sdf.parse(firstDateTimeStr.toString());
} catch (ParseException e) {
e.printStackTrace();
}
return firstDateTime;
}
测试结果:
@Test
void testFirstDayOfYear(){
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
// 获取当前时间
Date currentDate = getCurrentDate();
Date firstDayDateOfYear = getFirstDayDateOfYear(currentDate);
System.out.println("所在月第一天为:" + format.format(firstDayDateOfYear));
}
private Date getCurrentDate() {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
long currentTimeMillis = System.currentTimeMillis();
Date currentDate = new Date(currentTimeMillis);
System.out.println("当前时间为:" + format.format(currentDate));
return currentDate;
}
// 输出
//当前时间为:2021-09-28 09:23:28
//所在月第一天为:2021-01-01 00:00:00
1.4 获取当前时间所在年的最后一天
private static Date getLastDayOfYear(final Date date) {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
final Calendar cal = Calendar.getInstance();
cal.setTime(date);
final int last = cal.getActualMaximum(Calendar.DAY_OF_YEAR);
cal.set(Calendar.DAY_OF_YEAR, last);
Date time = cal.getTime();
return processDate(time);
}
private static Date processDate(Date time) {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String lastDate = df.format(time);
StringBuilder lastDateTimeStr = new StringBuilder().append(lastDate).append(" 23:59:59");
Date lastDateTime = null;
try {
lastDateTime = sdf.parse(lastDateTimeStr.toString());
} catch (ParseException e) {
e.printStackTrace();
}
return lastDateTime;
}
测试结果:
@Test
void testLastDayOfYear(){
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
// 获取当前时间
Date currentDate = getCurrentDate();
Date lastDayOfYear = getLastDayOfYear(currentDate);
System.out.println("所在年最后一天为:" + format.format(lastDayOfYear));
}
private Date getCurrentDate() {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
long currentTimeMillis = System.currentTimeMillis();
Date currentDate = new Date(currentTimeMillis);
System.out.println("当前时间为:" + format.format(currentDate));
return currentDate;
}
// 运行结果
// 当前时间为:2021-09-28 09:28:36
// 所在年最后一天为:2021-12-31 23:59:59
2.第二种实现方式(推荐,LocalDateTime类)
2.1 获取当前时间的月初,月末,年初,年末
private static LocalDateTime getFirstDayOfMonth(LocalDateTime localDateTime) {
return localDateTime.with(TemporalAdjusters.firstDayOfMonth()).withHour(0).withMinute(0).withSecond(0);
}
private static LocalDateTime getLastDayOfMonth(LocalDateTime localDateTime) {
return localDateTime.with(TemporalAdjusters.lastDayOfMonth()).withHour(23).withMinute(59).withSecond(59);
}
private static LocalDateTime getFirstDayOfYear(LocalDateTime localDateTime) {
return localDateTime.with(TemporalAdjusters.firstDayOfYear()).withHour(0).withMinute(0).withSecond(0);
}
private static LocalDateTime getLastDayOfYear(LocalDateTime localDateTime) {
return localDateTime.with(TemporalAdjusters.lastDayOfYear()).withHour(23).withMinute(59).withSecond(59);
}
