Java8新增日期类LocalDateTime,LocalDateTime与Date相比有什么优势

JDK8之前Date类

1.Date类概述和构造方法

2.Date的常用方法

public class DateDemo2 {
    public static void main(String[] args) {
        Date date1 = new Date();
        date1.setTime(0L);
        System.out.println(date1);
        //methods1();
    }

    public static void methods1() {
        //getTime():获取当前时间
        Date date1 = new Date();
        System.out.println(date1.getTime());
    }
}
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JDK8之前SimpleDateFormat类概述

SimpleDateFormat可以对Date对象，进行格式化和解析

1.SimpleDateFormat的构造方法

2.SimpleDateFormat格式化和解析日期

① 格式化（从Date到String）

• public String format(Date date):将日期格式化日期/时间字符串，把时间按照固定格式展示

② 解析（从String到Date）

• pubic Date parse(String source):从给定字符串的开始解析文本以生成文本，需要对时间进行计算

格式化

public class DateDemo3 {
    public static void main(String[] args) {
        Date date = new Date();
        //SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd HH时mm分ss秒");
        //SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd");
        //SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        String format = sdf.format(date);
        System.out.println(format);
    }
}
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解析

public class DateDemo4 {
    public static void main(String[] args) throws ParseException {
        String s = "2022-11-13";
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Date date = sdf.parse(s);
        System.out.println(date);
    }
}
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JDK8新增日期类

1.JDK8Date分类

2.LocalDateTime创建时间

public class JDK8DateDemo2 {
    public static void main(String[] args) throws ParseException {
        LocalDateTime now = LocalDateTime.now();
        System.out.println(now);
        LocalDateTime time = LocalDateTime.of(2020, 11, 1, 8, 10, 10);
        DateTimeFormatter dft = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        String format = time.format(dft);
        System.out.println(format);
    }
}
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3.LocalDateTime获取方法

public class JDK8DateDemo3 {
    public static void main(String[] args) throws ParseException {
        LocalDateTime dateTime = LocalDateTime.of(2020, 11, 12, 8, 10, 10);
        //public int getYear()
        int timeYear = dateTime.getYear();
        System.out.println("年为 " + timeYear);
        //public int getMonthValue()
        int monthValue = dateTime.getMonthValue();
        System.out.println("月为 " + monthValue);
        //public int getDayOfMonth()
        int dayOfMonth = dateTime.getDayOfMonth();
        System.out.println("月中第 " + dayOfMonth + "天");
        //public int getDayOfYear()
        int dayOfYear = dateTime.getDayOfYear();
        System.out.println("年中第 " + dayOfYear + "天");
        //public DayOfWeek getDayOfWeek()
        DayOfWeek dayOfWeek = dateTime.getDayOfWeek();
        System.out.println("星期为 " + dayOfWeek);
        //public int getHour()
        int hour = dateTime.getHour();
        System.out.println("小时为 " + hour);
        //public int getMinute()
        int minute = dateTime.getMinute();
        System.out.println("分钟为 " + minute);
        //public int getSecond()
        int second = dateTime.getSecond();
        System.out.println("秒为 " + second);
    }
}
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4.LocalDateTime转换方法

public class JDK8DateDemo4 {
    public static void main(String[] args) throws ParseException {
        LocalDateTime dateTime = LocalDateTime.of(2020, 11, 12, 8, 10, 10);
        LocalDate localDate = dateTime.toLocalDate();
        System.out.println(localDate);
        LocalTime localTime = dateTime.toLocalTime();
        System.out.println(localTime);
    }
}
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5.LocalDateTime格式化和解析

6.JDK8的日期格式化器：DateTimeFormatter

public class JDK8DateDemo5 {
    public static void main(String[] args) throws ParseException {
       method2();
       // method1();
    }

    public static void method2() {
        String s ="2008年08月07日 13:14:15";
        DateTimeFormatter pattern = DateTimeFormatter.ofPattern("yyyy年MM月dd日 HH:mm:ss");
        LocalDateTime date= LocalDateTime.parse(s, pattern);
        System.out.println(date);
    }

    public static void method1() {
        LocalDateTime dateTime = LocalDateTime.of(2020, 11, 12, 8, 10, 10);
        System.out.println(dateTime);
        DateTimeFormatter pattern = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        String date = dateTime.format(pattern);
        System.out.println(date);
    }
}
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7.LocalDateTime增加或者减少时间的方法

• 方法返回一个新的LocalDateTime对象，返回值就是修改之后的结果

• 参数为正，就是往后加

• 参数为负，就是往前减

public class JDK8DateDemo6 {
    public static void main(String[] args) throws ParseException {
        LocalDateTime dateTime = LocalDateTime.of(2020, 11, 12, 8, 10, 10);
        LocalDateTime nweDateTime = dateTime.plusYears(1);
        System.out.println(nweDateTime);
    }
}
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8.LocalDateTime修改方法

public class JDK8DateDemo7 {
    public static void main(String[] args) throws ParseException {
        LocalDateTime dateTime = LocalDateTime.of(2020, 11, 12, 8, 10, 10);
        LocalDateTime newDate = dateTime.withYear(2066);
        System.out.println(newDate);
        LocalDateTime dateTime1 = dateTime.withMonth(10);
        System.out.println(dateTime1);
    }
}
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Period类

public class JDK8DateDemo8 {
    public static void main(String[] args) throws ParseException {
        LocalDate dateTime1 = LocalDate.of(2020, 11, 12);
        LocalDate dateTime2 = LocalDate.of(2028, 10, 10);
        //public static Period between(LocalDate startDateInclusive, LocalDate endDateExclusive)
        Period period = Period.between(dateTime1, dateTime2);
        System.out.println(period);//P7Y10M28D
        //public int getYears() //这段时间的年数
        System.out.println(period.getYears());//7

        //public int getMonths()//这段时间的月数
        System.out.println(period.getMonths());//10
        //public int getDays()//这段时间的天数
        System.out.println(period.getDays());//28
        //  public long toTotalMonths()//这段时间的总月数
        System.out.println(period.toTotalMonths());//94
    }
}
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Duration

public class JDK8DateDemo9 {
    public static void main(String[] args) throws ParseException {
        LocalDateTime localDateTime1 = LocalDateTime.of(2020, 11, 12, 10, 13, 14);
        LocalDateTime localDateTime2 = LocalDateTime.of(2020, 11, 13, 12, 10, 15);

        Duration duration = Duration.between(localDateTime1, localDateTime2);
        System.out.println(duration);//PT25H57M1S
        // public long toHours(): 时间间隔的小时
        System.out.println(duration.toHours());//25

        // public long toMinutes(): 时间间隔的分钟
        System.out.println(duration.toMinutes());//1557

        //public long toSeconds(): 时间间隔的秒
        System.out.println(duration.toSeconds());93421

        //public long toMillis():时间间隔的毫秒
        System.out.println(duration.toMillis());//93421000

        //public long toNanos():时间间隔的纳秒
        System.out.println(duration.toNanos());//93421000
    }
}
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