1. Method 1: If it is java8, you can use LocalDate to get it
// 获取当前日期前一天的日期
LocalDate localDate = LocalDate.now().minusDays(1);//1代表提前多少天
// 获取时间字符串如: 2023-03-01
System.out.println(localDate.toString());
// 获取当前年如 2023
System.out.println(localDate.getYear());
// 获取当前月如 3
System.out.println(localDate.getMonthValue());
// 获取当前天如 1
System.out.println(localDate.getDayOfMonth());
//获取前一天的日期
String date = localDate.format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));//转为String类型
Convert LocalDate to a string in the specified format
method 1
LocalDate localDate = LocalDate.parse("2022-02-02");
String date = localDate.format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));
System.out.println(date); //2022-02-02
Method 2
LocalDate localDate = LocalDate.parse("2022-02-02");
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd");
String date = dtf.format(localDate);
System.out.println(date); //2022-02-02
2. Method 2: Use the Calendar class
//获取当前日期
Date date = new Date();
//将时间格式化成yyyy-MM-dd HH:mm:ss的格式
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
//创建Calendar实例
Calendar cal = Calendar.getInstance();
//设置当前时间
cal.setTime(date);
//在当前时间基础上减一年
cal.add(Calendar.YEAR, -1);
System.out.println(format.format(cal.getTime()));
//在当前时间基础上减一月
cal.add(Calendar.MONTH,-1);
System.out.println(format.format(cal.getTime()));
//同理增加一天的方法：
cal.add(Calendar.DATE, 1);
System.out.println(format.format(cal.getTime()));
3. Get the specified time
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");//定义日期显示格式
String now = sdf.format(new Date());//当前日期
String nowMonthLateDay = getNextDays(now, "-1");//当前日期的前一天
Calendar datees = Calendar.getInstance();
String years = String.valueOf(datees.get(Calendar.YEAR)) + "-11-15";//获取当前年的11-15
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");//定义日期显示格式
Calendar c = Calendar.getInstance();
c.add(Calendar.MONTH, -1);//当前月减去一个月
String before = sdf.format(c.getTime());//上个月的当前日期
String now = sdf.format(new Date());//当前日期
String nowMonthLateDay = getNextDay(now, "-1");//当前日期的前一天
String lateMonthLateDay = getNextDay(before, "-1");//上个月的当前日期的前一天
Calendar cal = Calendar.getInstance();
// int m=cal.get(Calendar.MONTH)+1;//获取当前月份
// System.err.println("当前月份:"+m);
String nowMonthFirstDay = getFirstDayOfMonth(1);//获取当前月份的第一天
cal.add(Calendar.MONTH, -1);
cal.set(Calendar.DAY_OF_MONTH, 1); //重写当前日期
String lateMonthFirstDay = sdf.format(cal.getTime());//获取上个月的第一天
4. Get the current year, if it exceeds a certain time, subtract one year or add one year
Date date = new Date();//获取日期
SimpleDateFormat dateFormats= new SimpleDateFormat("yyyy");//日期格式
String year=dateFormats.format(date);//获取当前年度
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd");
//把String转为LocalDate
LocalDate localTime=LocalDate.parse(year+"-06-30",dtf);
Integer years=Integer.valueOf(year);
if (!LocalDate.now().isAfter(localTime)){//判断时间是否超过
years=Integer.valueOf(year)-1;
}
System.err.println(years);
}
5. Tool class for getting time
/**
* 将短时间格式字符串转换为时间 yyyy-MM-dd
*
* @param strDate
* @return
*/
public static Date strToDate(String strDate) {
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
ParsePosition pos = new ParsePosition(0);
Date strtodate = formatter.parse(strDate, pos);
return strtodate;
}
/**
* 得到一个时间延后或前移几天的时间,nowdate为时间,delay为前移或后延的天数
*/
public static String getNextDay(String nowdate, String delay) {
try {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
String mdate = "";
Date d = strToDate(nowdate);
long myTime = (d.getTime() / 1000) + Integer.parseInt(delay) * 24 * 60 * 60;
d.setTime(myTime * 1000);
mdate = format.format(d);
return mdate;
} catch (Exception e) {
return "";
}
}
/**
* 得到一个时间延后或前移几天的时间,nowdate为时间,delay为前移或后延的天数
*/
public static String getNextDays(String nowdate, String delay) {
try {
SimpleDateFormat format = new SimpleDateFormat("-MM-dd");
String mdate = "";
Date d = strToDate(nowdate);
long myTime = (d.getTime() / 1000) + Integer.parseInt(delay) * 24 * 60 * 60;
d.setTime(myTime * 1000);
mdate = format.format(d);
return mdate;
} catch (Exception e) {
return "";
}
}
/**
* 获取当前小时
*
* @return
*/
public static String getTimeShort() {
SimpleDateFormat formatter = new SimpleDateFormat(" HH");
Date currentTime = new Date();
String dateString = formatter.format(currentTime);
return dateString;
}
/**
* 获取当前月第一天
*
* @param month
* @return
*/
public static String getFirstDayOfMonth(int month) {
Calendar calendar = Calendar.getInstance();
// 设置月份
calendar.set(Calendar.MONTH, month - 1);
// 获取某月最小天数
int firstDay = calendar.getActualMinimum(Calendar.DAY_OF_MONTH);
// 设置日历中月份的最小天数
calendar.set(Calendar.DAY_OF_MONTH, firstDay);
// 格式化日期
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String firstDays = sdf.format(calendar.getTime());
return firstDays;
}
//g过去年度
public static String gerLateYear(Integer num){
SimpleDateFormat format = new SimpleDateFormat("yyyy");
Calendar c = Calendar.getInstance();
//过去一年
c.setTime(new Date());
c.add(Calendar.YEAR, num);
Date y = c.getTime();
String year = format.format(y);
return year;
}
//判断是否超过指定时间
public static boolean afterDate(String date) {
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd");
//把String转为LocalDate
LocalDate localTime = LocalDate.parse(date, dtf);
//判断当前日期是否大于指定日期
return LocalDate.now().isAfter(localTime);
}