LocalDate的用法与String互转

古城微笑少年丶 2023-09-24 18:31 7阅读 0赞

一、LocalDate常用用法  
1.1、申明定义

LocalDate formatDate = LocalDate.of(2020, 2, 5); // 自定义  
LocalDate today = LocalDate.now(); // 获取当前日期  
1.2、getX() 获取年月日等

注意：获取月份使用getMonthValue()

System.out.println(formatDate.getMonth()); // FEBRUARY 获取所在月份（英文）  
System.out.println(formatDate.getMonthValue()); // 2 获取所在月份（英文）  
System.out.println(formatDate.getDayOfMonth()); // 5 获取所在天  
1.3、plusX()、minusX()

LocalDate nextDay = formatDate.plusDays(1);  
System.out.println(nextDay); // 2020-02-06 明天  
LocalDate nextWeek = formatDate.plusWeeks(1);  
System.out.println(nextWeek); // 2020-02-12 下周当天  
LocalDate lastMonth = formatDate.minusMonths(1);  
System.out.println(lastMonth); // 2020-01-05 上月当天  
1.4、扩展用法

常用于报表中计算同比环比等日期

// 同环比日期计算  
LocalDate firstWeekDay = formatDate.with(TemporalAdjusters.previous(DayOfWeek.MONDAY));  
System.out.println(firstWeekDay); // 2020-02-03 本周第一天  
LocalDate firstMonthDay = formatDate.with(TemporalAdjusters.firstDayOfMonth());  
System.out.println(firstMonthDay); // 2020-02-01 本月第一天  
LocalDate firstYearDay = formatDate.with(TemporalAdjusters.firstDayOfYear());  
System.out.println(firstYearDay); // 2020-01-01 本年第一天  
// 判断两个日期前后  
boolean param = formatDate.isBefore(today);  
System.out.println(param); // true 判断a是否早于b  
// 计算两个日期的间隔天数  
LocalDate start = LocalDate.parse("2019-12-01");  
LocalDate end = LocalDate.parse("2020-02-05");  
long days = start.until(end, ChronoUnit.DAYS);  
System.out.println("days: " + days); // days: 66  
二、LocalDate与String互转  
2.1、LocalDate转String

DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd");  
LocalDate formatDate = LocalDate.of(2020, 2, 5);  
String dateStr = formatDate.format(df);  
System.out.println("LocalDate => String: " + dateStr);  
2.2、String转LocalDate

DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd");  
LocalDate dateParam = LocalDate.parse(dateStr, df);  
System.out.println("String => LocalDate: " + dateParam);  
2.3 固定格式输出时间字符串

/\*\*  
\* 时间截取--日  
\*/  
private String timeSubStringDay(LocalDateTime sendTime) \{  
String localDateTimeStr = sendTime.format(DateTimeFormatter.ofPattern("MM-dd HH:mm"));  
return localDateTimeStr;  
\}  
三、代码实践  
import java.time.DayOfWeek;  
import java.time.LocalDate;  
import java.time.format.DateTimeFormatter;  
import java.time.temporal.TemporalAdjusters;  
  
/\*\*  
\* LocalDate日期转换  
\*  
\* @author: Tansj  
\* @since: 2020/02/08  
\*/  
public class Test \{  
  
public static void main(String\[\] args) \{  
LocalDate formatDate = LocalDate.of(2020, 2, 5);  
LocalDate today = LocalDate.now();  
System.out.println(formatDate); // 2020-02-05 当天  
System.out.println(today); // 2020-02-08 本日当天  
boolean param = formatDate.isBefore(today);  
System.out.println(param); // true 判断a是否早于b  
System.out.println("=========================================");  
System.out.println(formatDate.getMonth()); // FEBRUARY 获取所在月份（英文）  
System.out.println(formatDate.getMonthValue()); // 2 获取所在月份（数字）  
System.out.println(formatDate.getDayOfMonth()); // 5 获取所在天  
System.out.println("=========================================");  
LocalDate nextDay = formatDate.plusDays(1);  
System.out.println(nextDay); // 2020-02-06 明天  
LocalDate nextWeek = formatDate.plusWeeks(1);  
System.out.println(nextWeek); // 2020-02-12 下周当天  
LocalDate lastMonth = formatDate.minusMonths(1);  
System.out.println(lastMonth); // 2020-01-05 上月当天  
System.out.println("=========================================");  
LocalDate firstWeekDay = formatDate.with(TemporalAdjusters.previous(DayOfWeek.MONDAY));  
System.out.println(firstWeekDay); // 2020-02-03 本周第一天  
LocalDate firstMonthDay = formatDate.with(TemporalAdjusters.firstDayOfMonth());  
System.out.println(firstMonthDay); // 2020-02-01 本月第一天  
LocalDate firstYearDay = formatDate.with(TemporalAdjusters.firstDayOfYear());  
System.out.println(firstYearDay); // 2020-01-01 本年第一天  
System.out.println("=========================================");  
DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd");  
String dateStr = formatDate.format(df);  
System.out.println("LocalDate => String: " + dateStr); // LocalDate => String: 2020-02-05  
LocalDate dateParam = LocalDate.parse(dateStr, df);  
System.out.println("String => LocalDate: " + dateParam); // String => LocalDate: 2020-02-05  
LocalDate start = LocalDate.parse("2019-12-01");  
LocalDate end = LocalDate.parse("2020-02-05");  
long days = start.until(end, ChronoUnit.DAYS);  
System.out.println("days: " + days); // days: 66  
\}  
\}

获取日期中的字符串 如"02-03"

String time = hydrologyVO.getSendTime().format(DateTimeFormatter.ofPattern("MM-dd"));

一、LocalDateTime转换至String互转

LocalDateTime localDateTime=LocalDateTime.parse(dates,DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));  
String localDateTimeStr=LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));

二、LocalDateTime转换至Long互转

Long localDateTimeLong=Timestamp.valueOf(LocalDateTime.now()).getTime();  
LocalDateTime localDateTimeLongTime=LocalDateTime.ofInstant(Instant.ofEpochMilli(localDateTimeLong)  
  
public static void main(String\[\] args) \{  
DateTimeFormatter fmt = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");  
LocalDateTime localDateTime = LocalDateTime.now();  
String dateStr = localDateTime.format(fmt);  
System.out.println(dateStr);  
\}  
文章知识点与官方知识档案匹配，可进一步学习相关知识  
————————————————  
版权声明：本文为CSDN博主「月渐盈」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。  
原文链接：https://blog.csdn.net/qq\_34471241/article/details/121104081