Java 日期与时间API相关用法总结

public class DateTime01 {

  public static void main(String[] args) {

   long nowTime = System.currentTimeMillis() ;

   java.util.Date data01 = new java.util.Date(nowTime);

   java.sql.Date date02 = new java.sql.Date(nowTime);

   System.out.println(data01);

   System.out.println(date02.getTime());

  }

}

打印：

Fri Jan 29 15 : 11 : 25 CST 2021

1611904285848

public class DateTime02 {

  public static void main(String[] args) {

   Date nowDate = new Date();

   System.out.println( "年:" +nowDate.getYear());

   System.out.println( "月:" +nowDate.getMonth());

   System.out.println( "日:" +nowDate.getDay());

  }

}

public int getYear() {

  return normalize().getYear() - 1900 ;

}

public int getMonth() {

  return normalize().getMonth() - 1 ;

}

public int getDay() {

  return normalize().getDayOfWeek() - BaseCalendar.SUNDAY;

}

public class DateTime02 {

  public static void main(String[] args) throws Exception {

   // 默认转换

   DateFormat dateFormat01 = new SimpleDateFormat() ;

   String nowDate01 = dateFormat01.format( new Date()) ;

   System.out.println( "nowDate01=" +nowDate01);

   // 指定格式转换

   String format = "yyyy-MM-dd HH:mm:ss" ;

   SimpleDateFormat dateFormat02 = new SimpleDateFormat(format);

   String nowDate02 = dateFormat02.format( new Date()) ;

   System.out.println( "nowDate02=" +nowDate02);

   // 解析时间

   String parse = "yyyy-MM-dd HH:mm" ;

   SimpleDateFormat dateFormat03 = new SimpleDateFormat(parse);

   Date parseDate = dateFormat03.parse( "2021-01-18 16:59:59" ) ;

   System.out.println( "parseDate=" +parseDate);

  }

}

public class DateTime04 {

  public static void main(String[] args) {

   Calendar calendar = Calendar.getInstance();

   calendar.set(Calendar.YEAR, 2021 );

   calendar.set(Calendar.MONTH, 1 );

   calendar.set(Calendar.DAY_OF_MONTH, 12 );

   calendar.set(Calendar.HOUR_OF_DAY, 23 );

   calendar.set(Calendar.MINUTE, 59 );

   calendar.set(Calendar.SECOND, 59 );

   calendar.set(Calendar.MILLISECOND, 0 );

   DateFormat dateFormat = new SimpleDateFormat( "yyyy-MM-dd HH:mm:ss" ) ;

   Date defDate = calendar.getTime();

   System.out.println(defDate+ "||" +dateFormat.format(defDate));

  }

}

输出：Fri Feb 12 23 : 59 : 59 CST 2021 || 2021 - 02 - 12 23 : 59 : 59

public class DateTime05 {

  public static void main(String[] args) {

   // 日期：年-月-日

   System.out.println(LocalDate.now());

   // 时间：时-分-秒-毫秒

   System.out.println(LocalTime.now());

   // 日期时间：年-月-日 时-分-秒-毫秒

   System.out.println(LocalDateTime.now());

   // 日期节点获取

   LocalDate localDate = LocalDate.now();

   System.out.println( "[" + localDate.getYear() +

     "年]；[" + localDate.getMonthValue() +

     "月]；[" + localDate.getDayOfMonth()+ "日]" );

   // 计算方法

   System.out.println( "1年后：" + localDate.plusYears( 1 ));

   System.out.println( "2月前：" + localDate.minusMonths( 2 ));

   System.out.println( "3周后：" + localDate.plusWeeks( 3 ));

   System.out.println( "3天前：" + localDate.minusDays( 3 ));

   // 时间比较

   LocalTime localTime1 = LocalTime.of( 12 , 45 , 45 ); ;

   LocalTime localTime2 = LocalTime.of( 16 , 30 , 30 ); ;

   System.out.println(localTime1.isAfter(localTime2));

   System.out.println(localTime2.isAfter(localTime1));

   System.out.println(localTime2.equals(localTime1));

   // 日期和时间格式

   LocalDateTime localDateTime = LocalDateTime.now() ;

   LocalDate myLocalDate = localDateTime.toLocalDate();

   LocalTime myLocalTime = localDateTime.toLocalTime();

   System.out.println( "日期：" + myLocalDate);

   System.out.println( "时间：" + myLocalTime);

  }

}

public class DateTime06 {

  public static void main(String[] args) {

   // 精确到毫秒级别

   System.out.println(System.currentTimeMillis());

   System.out.println( new Date().getTime());

   System.out.println(Calendar.getInstance().getTime().getTime());

   System.out.println(LocalDateTime.now().toInstant(

     ZoneOffset.of( "+8" )).toEpochMilli());

  }

}

< dependency >

  < groupId >joda-time</ groupId >

  < artifactId >joda-time</ artifactId >

</ dependency >

public class JodaTimeUtil {

  // 时间格式

  public static final String DATE_FORMAT = "yyyy-MM-dd HH:mm:ss" ;

  private JodaTimeUtil (){}

  // 获取当前时间

  public static DateTime getCurrentTime (){

   return new DateTime() ;

  }

  // 获取指定时间

  public static DateTime getDateTime (Object obj){

   return new DateTime(obj) ;

  }

  // 把时间以指定格式转换为字符串

  public static String getNowDate (Date date, String format){

   return new DateTime(date).toString(format) ;

  }

  // 获取星期时间

  public static String getWeek (Object date){

   DateTime time = getDateTime (date) ;

   String week = null ;

   switch (time.getDayOfWeek()) {

    case DateTimeConstants.SUNDAY:

     week = "星期日" ;

     break ;

    case DateTimeConstants.MONDAY:

     week = "星期一" ;

     break ;

    case DateTimeConstants.TUESDAY:

     week = "星期二" ;

     break ;

    case DateTimeConstants.WEDNESDAY:

     week = "星期三" ;

     break ;

    case DateTimeConstants.THURSDAY:

     week = "星期四" ;

     break ;

    case DateTimeConstants.FRIDAY:

     week = "星期五" ;

     break ;

    case DateTimeConstants.SATURDAY:

     week = "星期六" ;

     break ;

    default :

     break ;

   }

   return week ;

  }

}