Java8日期时间处理

待我称王封你为后i 2023-09-23 20:39 139阅读 0赞

## 日期时间结构 ##

![在这里插入图片描述][36d918c01e4744d393ba63f8289ce401.png]

## 项目问题 ##

### 一，一天时间范围 ###

@Test  
public void mm() \{  
// 获取当前日期  
LocalDate nowDate = LocalDate.now();  
// 设置当天开始时间  
LocalDateTime beginTime = LocalDateTime.of(nowDate, LocalTime.MIN);  
Date start = Date.from( beginTime.atZone( ZoneId.systemDefault()).toInstant());  
System.out.println(start);  
// 设置当天的结束时间  
LocalDateTime endTime = LocalDateTime.of(nowDate, LocalTime.MAX);  
Date end = Date.from( endTime.atZone( ZoneId.systemDefault()).toInstant());  
System.out.println(end);  
\}

## 案例 ##

### 一，获取日期 ###

@Test  
public void aa() \{  
LocalDate localDate = LocalDate.now();  
System.out.println(localDate);  
System.out.println(localDate.getYear());  
System.out.println(localDate.getMonth().getValue());  
System.out.println(localDate.getDayOfWeek().getValue());  
\}

### 二，获取时间 ###

@Test  
public void nn() \{  
LocalTime localTime = LocalTime.now();  
// 获取小时  
int hour = localTime.getHour();  
int hour1 = localTime.get(ChronoField.HOUR\_OF\_DAY);  
// 获取分  
int minute = localTime.getMinute();  
int minute1 = localTime.get(ChronoField.MINUTE\_OF\_HOUR);  
// 获取秒  
int second = localTime.getSecond();  
int second1 = localTime.get(ChronoField.SECOND\_OF\_MINUTE);  
\}

### 三，获取日期时间 ###

@Test  
public void bb() \{  
LocalDateTime localDateTime = LocalDateTime.now();  
System.out.println(localDateTime);  
System.out.println(localDateTime.getYear());  
System.out.println(localDateTime.getMonth());  
System.out.println(localDateTime.getDayOfWeek());

### 四，获取带时区的日期时间 ###

@Test  
public void gg() \{  
ZonedDateTime zonedDateTime = ZonedDateTime.now();  
System.out.println(zonedDateTime);  
ZoneId zoneId = ZoneId.of(“America/New\_York”);  
LocalDateTime localDateTime = LocalDateTime.now();  
ZonedDateTime zonedDateTime1 = ZonedDateTime.of(localDateTime, zoneId);  
System.out.println(zonedDateTime1);  
\}

### 五，获取秒数 ###

@Test  
public void oo() \{  
// 创建Instant对象  
Instant instant = Instant.now();  
// 获取秒数  
long currentSecond = instant.getEpochSecond();  
// 获取毫秒数  
long currentMilli = instant.toEpochMilli();  
\}

### 六，获取时间戳 ###

// 在Java 8中获取当前的时间戳  
@Test  
public void jj() \{  
Instant timestamp = Instant.now();  
System.out.println("What is value of this instant " + timestamp.toEpochMilli());  
\}

### 七，处理特定日期 ###

// of  
@Test  
public void cc() \{  
LocalDate of = LocalDate.of(2018, 2, 2);  
System.out.println(of);  
LocalDateTime.of(LocalDate.now(), LocalTime.MAX);  
System.out.println(LocalTime.MAX);  
LocalDateTime of1 = LocalDateTime.of(2020, 2, 2, 02, 33, 22);  
System.out.println(of1);  
\}

### 八，时间调整和处理 ###

@Test  
public void pp() \{  
LocalDateTime now = LocalDateTime.now();  
// 一年中的五月  
LocalDateTime may = now.with(Month.MAY);  
// 月的某一天  
LocalDateTime dayOfMonth = now.with(ChronoField.DAY\_OF\_MONTH, 20);  
// 月的第一天  
LocalDateTime firstDayOfMonth = now.with(TemporalAdjusters.firstDayOfMonth());  
// 月的最后一天  
LocalDateTime result = now.with(Month.FEBRUARY).with(TemporalAdjusters.lastDayOfMonth());  
System.out.println(“一年中的五月”+may);  
System.out.println(“月的某一天”+dayOfMonth);  
System.out.println(“月的第一天”+firstDayOfMonth);  
System.out.println(“月的最后一天”+result);  
\}

### 九， 时间加减 ###

// 向前向后  
@Test  
public void dd() \{  
LocalDate localDate = LocalDate.now();  
System.out.println(localDate);  
// 向后  
LocalDate plus = localDate.plus(2, ChronoUnit.YEARS);  
System.out.println(plus);  
// 向前  
LocalDate minus = localDate.minus(2, ChronoUnit.YEARS);  
System.out.println(minus);  
\}

### 十，时钟 ###

// 时钟  
@Test  
public void ee() \{

System.out.println(System.currentTimeMillis());
    
    System.out.println(new Date().getTime());
    
    // java8
    // 根据您的系统时钟返回当前时间并设置为UTC。（默认）
    Clock clock = Clock.systemUTC();
    System.out.println("Clock : " + clock.millis());
    
    // Returns time based on system clock zone
    // 根据系统时钟区返回时间
    Clock defaultClock = Clock.systemDefaultZone();
    System.out.println("Clock : " + defaultClock.millis());

### 十一，判断日期是早还是晚某个时间 ###

// 判断日期是早还是晚某个时间  
@Test  
public void ff() \{  
LocalDate localDate = LocalDate.now();  
if (localDate.isBefore(LocalDate.of(2022, 2, 2))) \{  
System.out.println("localDate isBefore ");  
\}  
if (localDate.isAfter(LocalDate.of(2022, 2, 2))) \{  
System.out.println("localDate isAfter ");  
\}

### 十二，处理时区 ###

// 处理时区  
@Test  
public void gg() \{  
ZonedDateTime zonedDateTime = ZonedDateTime.now();  
System.out.println(zonedDateTime);  
ZoneId zoneId = ZoneId.of(“America/New\_York”);  
LocalDateTime localDateTime = LocalDateTime.now();  
ZonedDateTime zonedDateTime1 = ZonedDateTime.of(localDateTime, zoneId);  
System.out.println(zonedDateTime1);  
\}

### 十三，闰年 ###

// 闰年  
@Test  
public void hh() \{  
LocalDate localDate = LocalDate.now();  
if (localDate.isLeapYear()) \{  
System.out.println(“This year is Leap year”);  
\} else \{  
System.out.println(“This year is not a Leap year”);  
\}  
\}

### 十四，计算两个日期之间的天数和月数 ###

// 计算两个日期之间的天数和月数  
@Test  
public void ii() \{

LocalDate today = LocalDate.now();
    
    LocalDate java8Release = LocalDate.of(2018, 12, 14);
    
    Period periodToNextJavaRelease = Period.between(today, java8Release);
    
    System.out.println("Years left between today and Java 8 release : "
            + periodToNextJavaRelease.getYears() );
    
    System.out.println("Months left between today and Java 8 release : "
            + periodToNextJavaRelease.getMonths() );
    
    System.out.println("Days left between today and Java 8 release : "
            + periodToNextJavaRelease.getDays() );

### 十五，格式化时间 ###

// 格式化时间

> java8之前

SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
    System.out.println(simpleDateFormat.format(new Date()));

> java8

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
    System.out.println(LocalDate.now().format(formatter));
    
    DateTimeFormatter formatter1 = DateTimeFormatter.ofPattern("yyyy-MM-dd hh:mm:ss");
    System.out.println(LocalDateTime.now().format(formatter1));

### 十六，时间字符串互转 ###

// 时间字符串互转  
@Test  
public void ll() \{

/**
     * 时间转字符串
     */
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
    System.out.println(LocalDate.now().format(formatter));
    
    /**
     * 字符串转时间
     *      默认转换格式 2022-12-30
     */
    LocalDate parse = LocalDate.parse("2022-12-30");
    System.out.println(parse);
    
    DateTimeFormatter formatter1 = DateTimeFormatter.ofPattern("yyyy-MM-dd");
    LocalDate parse1 = LocalDate.parse("2022-12-30", formatter1);
    System.out.println(parse1);
    
    DateTimeFormatter formatter2 = DateTimeFormatter.ofPattern("yyyyMMdd");
    LocalDate parse2 = LocalDate.parse("20221230", formatter2);
    System.out.println(parse2);
    System.out.println(parse2.format(formatter2));

[36d918c01e4744d393ba63f8289ce401.png]: https://img-blog.csdnimg.cn/36d918c01e4744d393ba63f8289ce401.png