在实践中学习java（1）--JAVA8的LocalDateTi
一、JAVA8的LocalDateTime
最近写自动化用例遇到一个时间问题。获取当年开始时间和结束时间。
从上网搜索了使用Calendar方式获取：
public StringgetYearStart(){//当年开始时间戳，毫秒
Calendar calendar = Calendar.getInstance();// 获取当前日期
calendar.add(Calendar.YEAR, 0);
calendar.add(Calendar.MONTH, 0);
calendar.add(Calendar.DATE, 0);
calendar.set(Calendar.DAY_OF_YEAR, 1);
calendar.set(Calendar.HOUR, -12);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);
Long time = calendar.getTimeInMillis();
return String.valueOf(time);
}
//-------------------------------------------------------
public StringgetYearEnd(){//当年结束时间戳，毫秒
Calendar calendar = Calendar.getInstance();// 获取当前日期
calendar.add(Calendar.YEAR, 1);
calendar.add(Calendar.DATE, 0);
calendar.add(Calendar.MONTH, 0);
calendar.set(Calendar.DAY_OF_YEAR, -1);
calendar.set(Calendar.HOUR, 23);
calendar.set(Calendar.MINUTE, 59);
calendar.set(Calendar.SECOND, 59);
calendar.set(Calendar.MILLISECOND, 999);
Long time = calendar.getTimeInMillis();
return String.valueOf(time);
}
但这个方法有个问题，中午12点前执行和12点后执行，返回的时间不一样，差12个小时。
12点前执行，返回：1577764800248（2019/12/31 12:0:0）、 1609343999999（2020/12/30 23:59:59）
12点后执行，返回：1577808000000（2020/1/1 0:0:0）、 1609430399999（2020/12/31 23:59:59）
解决办法：使用java8的LocalDate和LocalDateTime方式：
/**
* @Description:当天的开始时间
* @Param: [today, isFirst: true 表示开始时间，false表示结束时间]
*/
public static StringgetStartOrEndDayOfDay(LocalDate today, Boolean isFirst){
LocalDate resDate = LocalDate.now();
if (today ==null) {
today = resDate;
}
if(isFirst){
return String.valueOf(LocalDateTime.of(today, LocalTime.MIN).toInstant(ZoneOffset.ofHours(8)).toEpochMilli());
}else{
return String.valueOf(LocalDateTime.of(today, LocalTime.MAX).toInstant(ZoneOffset.ofHours(8)).toEpochMilli());
}
}
/**
* @Description:本周的开始时间
* @Param: [today, isFirst: true 表示开始时间，false表示结束时间]
*/
public static StringgetStartOrEndDayOfWeek(LocalDate today, Boolean isFirst){
String time =MinTime;
LocalDate resDate = LocalDate.now();
if (today ==null) {
today = resDate;
}
DayOfWeek week = today.getDayOfWeek();
int value = week.getValue();
if (isFirst) {
resDate = today.minusDays(value -1);
}else {
resDate = today.plusDays(7 - value);
time =MaxTime;
}
LocalDateTime localDateTime = LocalDateTime.parse(resDate.toString() + time);
return String.valueOf(localDateTime.toInstant(ZoneOffset.ofHours(8)).toEpochMilli());
}
/**
* @Description:本月的开始时间
* @Param: [today, isFirst: true 表示开始时间，false表示结束时间]
*/
public static StringgetStartOrEndDayOfMonth(LocalDate today, Boolean isFirst){
String time =MinTime;
LocalDate resDate = LocalDate.now();
if (today ==null) {
today = resDate;
}
Month month = today.getMonth();
int length = month.length(today.isLeapYear());
if (isFirst) {
resDate = LocalDate.of(today.getYear(), month, 1);
}else {
resDate = LocalDate.of(today.getYear(), month, length);
time =MaxTime;
}
LocalDateTime localDateTime = LocalDateTime.parse(resDate.toString() + time);
return String.valueOf(localDateTime.toInstant(ZoneOffset.ofHours(8)).toEpochMilli());
}
/**
* @Description:本季度的开始时间
* @Param: [today, isFirst: true 表示开始时间，false表示结束时间]
*/
public static StringgetStartOrEndDayOfQuarter(LocalDate today, Boolean isFirst){
String time =MinTime;
LocalDate resDate = LocalDate.now();
if (today ==null) {
today = resDate;
}
Month month = today.getMonth();
Month firstMonthOfQuarter = month.firstMonthOfQuarter();
Month endMonthOfQuarter = Month.of(firstMonthOfQuarter.getValue() +2);
if (isFirst) {
resDate = LocalDate.of(today.getYear(), firstMonthOfQuarter, 1);
}else {
resDate = LocalDate.of(today.getYear(), endMonthOfQuarter, endMonthOfQuarter.length(today.isLeapYear()));
time =MaxTime;
}
LocalDateTime localDateTime = LocalDateTime.parse(resDate.toString() + time);
return String.valueOf(localDateTime.toInstant(ZoneOffset.ofHours(8)).toEpochMilli());
}
/**
* @Description:本年度的开始时间
* @Param: [today, isFirst: true 表示开始时间，false表示结束时间]
*/
public static StringgetStartOrEndDayOfYear(LocalDate today, Boolean isFirst){
String time =MinTime;
LocalDate resDate = LocalDate.now();
if (today ==null) {
today = resDate;
}
if (isFirst) {
resDate = LocalDate.of(today.getYear(), Month.JANUARY, 1);
}else {
resDate = LocalDate.of(today.getYear(), Month.DECEMBER, Month.DECEMBER.length(today.isLeapYear()));
time =MaxTime;
}
LocalDateTime localDateTime = LocalDateTime.parse(resDate.toString() + time);
return String.valueOf(localDateTime.toInstant(ZoneOffset.ofHours(8)).toEpochMilli());
}
/**
* @Description:上个月的开始时间
* @Param: [today, isFirst: true 表示开始时间，false表示结束时间]
*/
public static StringgetStartOrEndDayOfLastMonth(LocalDate today, Boolean isFirst){
String time =MinTime;
LocalDate resDate = LocalDate.now();
if (today ==null) {
today = resDate;
}
today = today.minusMonths(1);
Month month = today.getMonth();
int length = month.length(today.isLeapYear());
if (isFirst) {
resDate = LocalDate.of(today.getYear(), month, 1);
}else {
resDate = LocalDate.of(today.getYear(), month, length);
time =MaxTime;
}
LocalDateTime localDateTime = LocalDateTime.parse(resDate.toString() + time);
return String.valueOf(localDateTime.toInstant(ZoneOffset.ofHours(8)).toEpochMilli());
}
/**
* @Description:当天往前30天的开始和结束时间
* @Param: [today, isFirst: true 表示开始时间，false表示结束时间]
*/
public static StringgetBefore30Days(LocalDate today, Boolean isFirst){
LocalDate resDate = LocalDate.now();
if (today ==null) {
today = resDate;
}
today = today.minusDays(30);
if(isFirst){
return String.valueOf(LocalDateTime.of(today, LocalTime.MIN).toInstant(ZoneOffset.ofHours(8)).toEpochMilli());
}else{
return String.valueOf(LocalDateTime.of(today, LocalTime.MAX).toInstant(ZoneOffset.ofHours(8)).toEpochMilli());
}
}
/**
* @Description:当前往前12个月的开始时间-1号
* @Param: [today, isFirst: true 表示开始时间，false表示结束时间]
*/
public static StringgetBefore12Months(LocalDate today, Boolean isFirst){
String time =MinTime;
LocalDate resDate = LocalDate.now();
if (today ==null) {
today = resDate;
}
today = today.minusMonths(12);
Month month = today.getMonth();
int length = month.length(today.isLeapYear());
if (isFirst) {
resDate = LocalDate.of(today.getYear(), month, 1);
}else {
resDate = LocalDate.of(today.getYear(), month, length);
time =MaxTime;
}
LocalDateTime localDateTime = LocalDateTime.parse(resDate.toString() + time);
return String.valueOf(localDateTime.toInstant(ZoneOffset.ofHours(8)).toEpochMilli());
}
/**
* @Description:当前往前6年的开始时间
* @Param: [today, isFirst: true 表示开始时间，false表示结束时间]
*/
public static StringgetBefore6years(LocalDate today, Boolean isFirst){
String time =MinTime;
LocalDate resDate = LocalDate.now();
if (today ==null) {
today = resDate;
}
today = today.minusYears(6);
if (isFirst) {
resDate = LocalDate.of(today.getYear(), Month.JANUARY, 1);
}else {
resDate = LocalDate.of(today.getYear(), Month.DECEMBER, Month.DECEMBER.length(today.isLeapYear()));
time =MaxTime;
}
LocalDateTime localDateTime = LocalDateTime.parse(resDate.toString() + time);
return String.valueOf(localDateTime.toInstant(ZoneOffset.ofHours(8)).toEpochMilli());
}
二、static关键字
在《Java编程思想》P86页有这样一段话：
“static方法就是没有this的方法。在static方法内部不能调用非静态方法，反过来是可以的。而且可以在没有创建任何对象的前提下，仅仅通过类本身来调用static方法。这实际上正是static方法的主要用途。”
这篇文章分析的特别好，可仔细阅读一遍：https://www.cnblogs.com/dolphin0520/p/3799052.html
