4. java 中的时间日期

一.Date 类

import java.util.Date;

public class TimeDateTest {

    public static void main(String[] args) {
        //1. currentTimeMillis ,当前时间戳
        long t1 = System.currentTimeMillis();
        System.out.println(t1);
        /*
        * java.util.Date 类
        *           ----java.sql.Date
        * 1.两个构造器的使用
        * Date()
        * Date(String s)
        * 2.两个方法的使用
        * date1.toString()
        * date1.getTime() 获取当前Date对象对应的毫秒数
        *
        * */
        Date date1 = new Date();
        System.out.println(date1); //Sun Jul 19 09:29:44 CST 2020
        long time = date1.getTime();
        System.out.println(time); // 获取时间戳  1595122229833
        String s = date1.toString();
        System.out.println(s); //Sun Jul 19 09:31:50 CST 2020
        //
        Date date2 = new Date("Sun Jul 19 09:29:44 CST 2020");
        System.out.println(date2.getTime());

    }
}

二.java.text.simpleDateFormat 对日期Date解析格式化

import org.junit.Test;

import javax.sound.midi.Soundbank;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class TimeDateTest {

    public static void main(String[] args) {
        //1. currentTimeMillis ,当前时间戳
        long t1 = System.currentTimeMillis();
        System.out.println(t1);
        /*
        * java.util.Date 类
        *           ----java.sql.Date
        * 1.两个构造器的使用
        * Date()
        * Date(String s)
        * 2.两个方法的使用
        * date1.toString()
        * date1.getTime() 获取当前Date对象对应的毫秒数
        *
        * */
        Date date1 = new Date();
        System.out.println(date1); //Sun Jul 19 09:29:44 CST 2020
        long time = date1.getTime();
        System.out.println(time); // 获取时间戳  1595122229833
        String s = date1.toString();
        System.out.println(s); //Sun Jul 19 09:31:50 CST 2020
        //
        Date date2 = new Date("Sun Jul 19 09:29:44 CST 2020");
        System.out.println(date2.getTime());

    }

    @Test
    public void test1() throws ParseException {
        /*
        * java.text.simpleDateFormat
        * 对日期Date 类的格式化和解析
        *
        * */
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        Date date1 = sdf.parse("2020-12-01 12:23:23");

        System.out.println(date1); //Tue Dec 01 00:23:23 CST 2020
        System.out.println(date1.getTime());//1606753403000
        // java.sql.Date  通过时间戳将Date 时间转化为sql.Date
        java.sql.Date brithday = new java.sql.Date(date1.getTime());


    }
}

三.Calendar 

@Test
    public void test2(){

        // 创建其子类（GregorianCalendar）的对象或调用静态方法
        Calendar calendar = Calendar.getInstance();
        System.out.println(calendar.getClass());//class java.util.GregorianCalendar
        //常用方法
        // get()
        int  day = calendar.get(Calendar.DAY_OF_MONTH);
        System.out.println(day);//这个月的第几天  19
        int weeknum = calendar.get(Calendar.WEEK_OF_MONTH);// 这个月的第几周
        System.out.println(weeknum);//4

        // set()可变性
        calendar.set(Calendar.DAY_OF_MONTH,22);// 设置日期
        System.out.println(calendar.getTime());
        //add()
        calendar.add(Calendar.DAY_OF_MONTH,2);
        int days = calendar.get(Calendar.DAY_OF_MONTH);
        System.out.println(days);
        //Date --> 日期类
        Date date3 = new Date();
        calendar.setTime(date3);

        // 日历类转化为Date
        Date time = calendar.getTime();
        System.out.println(time);//Sun Jul 19 16:53:25 CST 2020



    }

四.LocalDate ,LocalTime,LocalDateTime

@Test
    public void test4(){
        // LocalDate ,LocalTime,LocalDateTime
        // now() 获取当前日期或时间
        LocalDate localdate = LocalDate.now();
        LocalTime localtime = LocalTime.now();
        LocalDateTime localdatetime = LocalDateTime.now();
        System.out.println(localdate);//2020-07-19
        System.out.println(localtime);//17:13:24.761
        System.out.println(localdatetime);//2020-07-19T17:13:24.761
        // of()设定指定年月日时分秒
        LocalDateTime localdatetime1 = LocalDateTime.of(2020,12,13,11,30,45);
        System.out.println(localdatetime1);//2020-12-13T11:30:45

        // getXXX() 获取相关属性
        int dayOfMonth = localdatetime1.getDayOfMonth();
        int monthValue = localdatetime1.getMonthValue();
        System.out.println(dayOfMonth);//13
        System.out.println(monthValue);//12
        DayOfWeek dayOfWeek = localdatetime1.getDayOfWeek();
        System.out.println(dayOfWeek);//SUNDAY

        // 设置相关属性with()
        LocalDate localdate3 = LocalDate.now();
        LocalDate localdate1 = localdate3.withDayOfMonth(25);
        System.out.println(localdate1);//2020-07-25

        LocalDateTime localDateTime4= LocalDateTime.now();
        LocalDateTime localDateTime = localDateTime4.withHour(18);
        System.out.println(localDateTime);//SUNDAY


    }

 代码：

import org.junit.Test;

import javax.sound.midi.Soundbank;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.time.*;
import java.util.Calendar;
import java.util.Date;

public class TimeDateTest {

    public static void main(String[] args) {
        //1. currentTimeMillis ,当前时间戳
        long t1 = System.currentTimeMillis();
        System.out.println(t1);
        /*
        * java.util.Date 类
        *           ----java.sql.Date
        * 1.两个构造器的使用
        * Date()
        * Date(String s)
        * 2.两个方法的使用
        * date1.toString()
        * date1.getTime() 获取当前Date对象对应的毫秒数
        *
        * */
        Date date1 = new Date();
        System.out.println(date1); //Sun Jul 19 09:29:44 CST 2020
        long time = date1.getTime();
        System.out.println(time); // 获取时间戳  1595122229833
        String s = date1.toString();
        System.out.println(s); //Sun Jul 19 09:31:50 CST 2020
        //
        Date date2 = new Date("Sun Jul 19 09:29:44 CST 2020");
        System.out.println(date2.getTime());

    }

    @Test
    public void test1() throws ParseException {
        /*
        * java.text.simpleDateFormat
        * 对日期Date 类的格式化和解析
        *
        * */
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        Date date1 = sdf.parse("2020-12-01 12:23:23");

        System.out.println(date1); //Tue Dec 01 00:23:23 CST 2020
        System.out.println(date1.getTime());//1606753403000
        // java.sql.Date  通过时间戳将Date 时间转化为sql.Date
        java.sql.Date brithday = new java.sql.Date(date1.getTime());


    }

    @Test
    public void test2(){

        // 创建其子类（GregorianCalendar）的对象或调用静态方法
        Calendar calendar = Calendar.getInstance();
        System.out.println(calendar.getClass());//class java.util.GregorianCalendar
        //常用方法
        // get()
        int  day = calendar.get(Calendar.DAY_OF_MONTH);
        System.out.println(day);//这个月的第几天  19
        int weeknum = calendar.get(Calendar.WEEK_OF_MONTH);// 这个月的第几周
        System.out.println(weeknum);//4

        // set()可变性
        calendar.set(Calendar.DAY_OF_MONTH,22);// 设置日期
        System.out.println(calendar.getTime());
        //add()
        calendar.add(Calendar.DAY_OF_MONTH,2);
        int days = calendar.get(Calendar.DAY_OF_MONTH);
        System.out.println(days);
        //Date --> 日期类
        Date date3 = new Date();
        calendar.setTime(date3);

        // 日历类转化为Date
        Date time = calendar.getTime();
        System.out.println(time);//Sun Jul 19 16:53:25 CST 2020
    }
    @Test
    public void test4(){
        // LocalDate ,LocalTime,LocalDateTime
        // now() 获取当前日期或时间
        LocalDate localdate = LocalDate.now();
        LocalTime localtime = LocalTime.now();
        LocalDateTime localdatetime = LocalDateTime.now();
        System.out.println(localdate);//2020-07-19
        System.out.println(localtime);//17:13:24.761
        System.out.println(localdatetime);//2020-07-19T17:13:24.761
        // of()设定指定年月日时分秒
        LocalDateTime localdatetime1 = LocalDateTime.of(2020,12,13,11,30,45);
        System.out.println(localdatetime1);//2020-12-13T11:30:45

        // getXXX() 获取相关属性
        int dayOfMonth = localdatetime1.getDayOfMonth();
        int monthValue = localdatetime1.getMonthValue();
        System.out.println(dayOfMonth);//13
        System.out.println(monthValue);//12
        DayOfWeek dayOfWeek = localdatetime1.getDayOfWeek();
        System.out.println(dayOfWeek);//SUNDAY

        // 设置相关属性with()
        LocalDate localdate3 = LocalDate.now();
        LocalDate localdate1 = localdate3.withDayOfMonth(25);
        System.out.println(localdate1);//2020-07-25

        LocalDateTime localDateTime4= LocalDateTime.now();
        LocalDateTime localDateTime = localDateTime4.withHour(18);
        System.out.println(localDateTime);//SUNDAY


    }
}