6.1.2 本地日期时间-Java语言基础9-常用API和常见算法

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- LocalDate 表示本地日期，LocalTime 表示本地时间，而 LocalDateTIme 表示本地日期时间。
- Instant 表示瞬间（本地日期时间），精确到纳秒。
LocalDateTIme 和 Instant 的区别：
- Instant 是带时区的（以UTC为准），用来替换以前的 Date 。
- LocalDateTIme 是不带时区（以本地时区为准）的，用来替换以前的 Calendar。
-  以 LocalDateTime 为例： 
-  获取对象： 
  - ① 获取当前日期时间：

```  
public static LocalDateTime now() {}
public static LocalDateTime now(ZoneId zone) {}
```
  ② 根据指定日期时间创建对象：
```
public static LocalDateTime of(int year, Month month, int dayOfMonth, int hour, int minute) {}
```
-  获取日期时间中的每个值： 
  - 获取年份：

```
public int getYear() {}
```
获取月份（1~12）：
```
public int getMonthValue() {}
```
获取月份的第几天（1~31）：
```
public int getDayOfMonth() {}
```
获取一年中的第几天（1~366）：
```
public int getDayOfYear() {}
```
获取星期：
```
public DayOfWeek getDayOfWeek() {}
```
获取小时：
```
public int getHour() {}
```

获取分钟：
```
public int getMinute() {}
```
获取秒：
```
public int getMinute() {}
```
获取纳秒：
```
public int getSecond() {}
```
转换为 LocalDate ：
```
public LocalDate toLocalDate() {}
```
转换为 LocalTime ：
```
public LocalTime toLocalTime()
```
修改年：
```
public LocalDateTime withYear(int year) {}
```
修改月：
```
public LocalDateTime withMonth(int month) {}
```
修改日期（一个月中的第几天）：
```
public LocalDateTime withDayOfMonth(int dayOfMonth) {}
```
修改日期（一年中的第几天）：
```
public LocalDateTime withDayOfYear(int dayOfYear) {}
```
修改小时：
```
public LocalDateTime withHour(int hour) {}
```
修改分钟：
```
public LocalDateTime withMinute(int minute) {}
```
修改秒：
```
public LocalDateTime withSecond(int second) {}
```
增加年或减少年：
```
public LocalDateTime plusYears(long years) {}
```
增加或减少月：
```
public LocalDateTime plusMonths(long months) {}
```
增加或减少日：
```
public LocalDateTime plusDays(long days) {}
```
增加或减少小时：
```
public LocalDateTime plusHours(long hours) {}
```
增加或减少分钟：
```
public LocalDateTime plusMinutes(long minutes) {}
```
增加或减少秒：
```
public LocalDateTime plusSeconds(long seconds) {}
```
增加或减少周：
```
public LocalDateTime plusWeeks(long weeks) {}
```
减少或添加年：
```
public LocalDateTime minusYears(long years) {}
```
减少或添加月：
```
public LocalDateTime minusMonths(long months) {}
```
减少或添加日：
```
public LocalDateTime minusDays(long days) {}
```
减少或添加小时：
```
public LocalDateTime minusHours(long hours) {}
```
减少或添加分钟：
```
public LocalDateTime minusMinutes(long minutes) {}
```
减少或添加秒：
```
public LocalDateTime minusSeconds(long seconds) {}
```
减少或添加周：
```
public LocalDateTime minusWeeks(long weeks) {}
```
是否在另一个时间之前：
```
public boolean isBefore(ChronoLocalDateTime<?> other) {}
```
两个时间是否相等：
```
public boolean isEqual(ChronoLocalDateTime<?> other) {}
```
是否在另一个时间之后：
```
public boolean isAfter(ChronoLocalDateTime<?> other) {}
```

示例：

```bash
package com.github.date.jdk8.demo1;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;

/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        
        LocalDate now = LocalDate.now();
        System.out.println("now = " + now); // now = 2021-09-26
        
        LocalTime now1 = LocalTime.now();
        System.out.println("now1 = " + now1); // now1 = 20:02:32.659
        
        LocalDateTime now2 = LocalDateTime.now();
        System.out.println("now2 = " + now2); // now2 = 2021-09-26T20:02:32.660
    }
}
```

示例：
```
package com.github.date.jdk8.demo9;

import java.time.Instant;
import java.time.LocalDateTime;

/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        
        Instant now = Instant.now(); 
        System.out.println("now = " + now); // now = 2021-09-27T01:54:39.351Z
        
        LocalDateTime now1 = LocalDateTime.now();
        System.out.println("now1 = " + now1); // now1 = 2021-09-27T09:54:39.401
    }
}
```
示例：

```
package com.github.date.jdk8.demo3;

import java.time.LocalDateTime;

/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        LocalDateTime of = LocalDateTime.of(2021, 11, 11, 11, 11, 11);
        System.out.println("of = " + of); // of = 2021-11-11T11:11:11
    }
}
```

示例：
```
package com.github.date.jdk8.demo4;

import java.time.DayOfWeek;
import java.time.LocalDateTime;

/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        LocalDateTime now = LocalDateTime.now();
        
        int year = now.getYear();
        System.out.println("获取年份：" + year);
        
        int monthValue = now.getMonthValue();
        System.out.println("获取月份：" + monthValue);
        
        int dayOfMonth = now.getDayOfMonth();
        System.out.println("获取天数：" + dayOfMonth);
        
        int dayOfYear = now.getDayOfYear();
        System.out.println("获取一年中的第" + dayOfYear + "天");
        
        DayOfWeek dayOfWeek = now.getDayOfWeek();
        System.out.println("获取星期" + dayOfWeek.getValue());
        
        int hour = now.getHour();
        System.out.println("获取小时:" + hour);
        
        int minute = now.getMinute();
        System.out.println("获取分钟：" + minute);
        
        int second = now.getSecond();
        System.out.println("获取秒：" + second);
        
        int nano = now.getNano();
        System.out.println("获取纳秒：" + nano);
    }
}
```
示例：
```
package com.github.date.jdk8.demo5;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;

/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        LocalDateTime now = LocalDateTime.now();
        
        // 转换为LocalDate
        LocalDate localDate = now.toLocalDate();
        System.out.println("localDate = " + localDate);
        
        // 转换为LocalTime
        LocalTime localTime = now.toLocalTime();
        System.out.println("localTime = " + localTime);
    }
}
```

示例：
```
package com.github.date.jdk8.demo9;

import java.time.LocalDateTime;

/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        
        LocalDateTime now = LocalDateTime.now();
        System.out.println("now = " + now); // now = 2021-09-27T08:41:04.197
        
        LocalDateTime localDateTime = now.withYear(2022);
        System.out.println("修改年 = " + localDateTime); // 修改年 = 2022-09-27T08:41:04.197
        
        LocalDateTime localDateTime1 = now.withMonth(10);
        System.out.println("修改月 = " + localDateTime1); // 修改月 = 2021-10-27T08:41:04.197
        
        LocalDateTime localDateTime2 = now.withDayOfMonth(28);
        System.out.println("修改日期（一个月中的第几天） = " + localDateTime2); // 修改日期（一个月中的第几天） = 2021-09-28T08:41:04.197
        
        LocalDateTime localDateTime3 = now.withDayOfYear(15);
        System.out.println("修改日期（一年中的第几天） = " + localDateTime3); // 修改日期（一年中的第几天） = 2021-01-15T08:41:04.197
        
        LocalDateTime localDateTime4 = now.withHour(10);
        System.out.println("修改小时 = " + localDateTime4); // 修改小时 = 2021-09-27T10:41:04.197
        
        LocalDateTime localDateTime5 = now.withMinute(15);
        System.out.println("修改分钟 = " + localDateTime5); // 修改分钟 = 2021-09-27T08:15:04.197
        
        LocalDateTime localDateTime6 = now.withSecond(10);
        System.out.println("修改秒 = " + localDateTime6); // 修改秒 = 2021-09-27T08:41:10.197
    }
}
```
示例：

```
package com.github.date.jdk8.demo7;

import java.time.LocalDateTime;

/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        
        LocalDateTime now = LocalDateTime.now();
        System.out.println("now = " + now); // now = 2021-09-27T09:30:21.527
        
        LocalDateTime localDateTime = now.plusYears(1);
        System.out.println("localDateTime = " + localDateTime); // localDateTime = 2022-09-27T09:30:21.527
        
        LocalDateTime localDateTime1 = now.plusYears(-1);
        System.out.println("localDateTime1 = " + localDateTime1); // localDateTime1 = 2020-09-27T09:30:21.527
        
        LocalDateTime localDateTime2 = now.plusMonths(1);
        System.out.println("localDateTime2 = " + localDateTime2); // localDateTime2 = 2021-10-27T09:30:21.527
        
        LocalDateTime localDateTime3 = now.plusDays(1);
        System.out.println("localDateTime3 = " + localDateTime3); // localDateTime3 = 2021-09-28T09:30:21.527
        
        LocalDateTime localDateTime4 = now.plusHours(1);
        System.out.println("localDateTime4 = " + localDateTime4); // localDateTime4 = 2021-09-27T10:30:21.527
        
        LocalDateTime localDateTime5 = now.plusMinutes(1);
        System.out.println("localDateTime5 = " + localDateTime5); // localDateTime5 = 2021-09-27T09:31:21.527
        
        LocalDateTime localDateTime6 = now.plusSeconds(1);
        System.out.println("localDateTime6 = " + localDateTime6); // localDateTime6 = 2021-09-27T09:30:22.527
        
        LocalDateTime localDateTime7 = now.plusWeeks(1);
        System.out.println("localDateTime7 = " + localDateTime7); // localDateTime7 = 2021-10-04T09:30:21.527
    }
}
```

示例：
```
package com.github.date.jdk8.demo8;

import java.time.LocalDateTime;

/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        LocalDateTime now = LocalDateTime.now();
        System.out.println("now = " + now); // now = 2021-09-27T09:39:01.406
        
        LocalDateTime localDateTime = now.minusYears(1);
        System.out.println("localDateTime = " + localDateTime); // localDateTime = 2020-09-27T09:39:01.406
        
        LocalDateTime localDateTime1 = now.minusMonths(1);
        System.out.println("localDateTime1 = " + localDateTime1); // localDateTime1 = 2021-08-27T09:39:01.406
        
        LocalDateTime localDateTime2 = now.minusDays(1);
        System.out.println("localDateTime2 = " + localDateTime2); // localDateTime2 = 2021-09-26T09:39:01.406
        
        LocalDateTime localDateTime3 = now.minusHours(1);
        System.out.println("localDateTime3 = " + localDateTime3); // localDateTime3 = 2021-09-27T08:39:01.406
        
        LocalDateTime localDateTime4 = now.minusMinutes(1);
        System.out.println("localDateTime4 = " + localDateTime4); // localDateTime4 = 2021-09-27T09:38:01.406
        
        LocalDateTime localDateTime5 = now.minusSeconds(1);
        System.out.println("localDateTime5 = " + localDateTime5); // localDateTime5 = 2021-09-27T09:39:00.406
        
        LocalDateTime localDateTime6 = now.minusWeeks(1);
        System.out.println("localDateTime6 = " + localDateTime6); // localDateTime6 = 2021-09-20T09:39:01.406
    }
}
```
示例：
```
package com.github.date.jdk8.demo10;

import java.time.LocalDateTime;

/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        
        LocalDateTime now = LocalDateTime.now();
        LocalDateTime localDateTime = LocalDateTime.now().plusHours(1);

System.out.println(now.isBefore(localDateTime)); // true
        System.out.println(now.isAfter(localDateTime)); // false
        System.out.println(now.isEqual(localDateTime)); // false
    }
}
```

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