java成神之——date和calendar日期的用法

• date和calendar日期的用法
  • util的data转换成sql的data
  • 创建Date对象
  • 格式化
  • Instant
  • ChronoUnit
  • LocalTime
  • LocalDate
• LocalDateTime
  • Date转换成字符串
  • 字符串转换成Date
  • 比较日期大小
  • 时区
  • Calendar

date和calendar日期的用法

util的data转换成sql的data

java.util.Date utilDate = new java.util.Date();
java.sql.Date sDate = new java.sql.Date(uDate.getTime());

创建Date对象

Date date = new Date();
System.out.println(date);

Calendar calendar = Calendar.getInstance();
calendar.set(90, Calendar.DECEMBER, 11);
Date myBirthDate = calendar.getTime();
System.out.println(myBirthDate); 

calendar.set(90, Calendar.DECEMBER, 11, 8, 32, 35);
Date myBirthDatenTime = calendar.getTime();
System.out.println(myBirthDatenTime);

格式化

String formatString = "yyyy/MM/dd hh:mm.ss";
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(formatString);

Date date = Calendar.getInstance().getTime();
String formattedDate = simpleDateFormat.format(date);

Instant

Instant now = Instant.now();
Instant epoch1 = Instant.ofEpochMilli(0);
Instant epoch2 = Instant.parse("1970-01-01T00:00:00Z");
java.time.temporal.ChronoUnit.MICROS.between(epoch1, epoch2);

ChronoUnit

时间间隔

LocalTime start = LocalTime.of(1, 0, 0); // hour, minute, second
LocalTime end = LocalTime.of(2, 10, 20); // hour, minute, second

long halfDays1 = start.until(end, ChronoUnit.HALF_DAYS); // 0
long halfDays2 = ChronoUnit.HALF_DAYS.between(start, end); // 0

long hours1 = start.until(end, ChronoUnit.HOURS); // 1
long hours2 = ChronoUnit.HOURS.between(start, end); // 1

long minutes1 = start.until(end, ChronoUnit.MINUTES); // 70
long minutes2 = ChronoUnit.MINUTES.between(start, end); // 70

long seconds1 = start.until(end, ChronoUnit.SECONDS); // 4220
long seconds2 = ChronoUnit.SECONDS.between(start, end); // 4220

long millisecs1 = start.until(end, ChronoUnit.MILLIS); // 4220000
long millisecs2 = ChronoUnit.MILLIS.between(start, end); // 4220000
long microsecs1 = start.until(end, ChronoUnit.MICROS); // 4220000000
long microsecs2 = ChronoUnit.MICROS.between(start, end); // 4220000000
long nanosecs1 = start.until(end, ChronoUnit.NANOS); // 4220000000000
long nanosecs2 = ChronoUnit.NANOS.between(start, end); // 4220000000000

LocalTime

只有时

基本用法
    LocalTime time = LocalTime.now();
    time = LocalTime.MIDNIGHT;
    time = LocalTime.NOON;
    time = LocalTime.of(12, 12, 45);

    time.plusMinutes(1);
    time.getMinutes();
    time.minusMinutes(1);

转换成Data
    LocalTime lTime = LocalTime.now();
    Instant instant = lTime.atDate(LocalDate.of(A_YEAR, A_MONTH, A_DAY)).
    atZone(ZoneId.systemDefault()).toInstant();
    Date time = Date.from(instant);

LocalDate

没有时

基本用法
    LocalDate lDate = LocalDate.now();
    lDate = LocalDate.of(2017, 12, 15);
    lDate = LocalDate.parse("2017-12-15");

    LocalDate.now(ZoneId.systemDefault());

LocalData转换成Data
    Date date = Date.from(Instant.now());
    ZoneId defaultZoneId = ZoneId.systemDefault();
    LocalDate localDate = date.toInstant().atZone(defaultZoneId).toLocalDate();

    Date.from(localDate.atStartOfDay(defaultZoneId).toInstant());

其他用法
    LocalDate tomorrow = LocalDate.now().plusDays(1);
    LocalDateTime anHourFromNow = LocalDateTime.now().plusHours(1);
    Long daysBetween = java.time.temporal.ChronoUnit.DAYS.between(LocalDate.now(),
    LocalDate.now().plusDays(3)); // 3
    Duration duration = Duration.between(Instant.now(),
    ZonedDateTime.parse("2016-07-27T07:00:00+01:00[Europe/Stockholm]"))

LocalDateTime

基本用法
    LocalDateTime lDateTime = LocalDateTime.now();
    lDateTime = LocalDateTime.of(2017, 12, 15, 11, 30);
    lDateTime = LocalDateTime.parse("2017-12-05T11:30:30");

    LocalDateTime.now(ZoneId.systemDefault());

LocalDateTime转换成Data
    Date date = Date.from(Instant.now());
    ZoneId defaultZoneId = ZoneId.systemDefault();
    LocalDateTime localDateTime = date.toInstant().atZone(defaultZoneId).toLocalDateTime();
    Date out = Date.from(localDateTime.atZone(defaultZoneId).toInstant());

其他用法
    LocalDateTime ldp1 = LocalDateTime.parse("2014-03-25T01:30");
    String pattern = "d-MM-yyyy HH:mm";
    DateTimeFormatter dtF1 = DateTimeFormatter.ofPattern(pattern);
    ldp2 = LocalDateTime.parse("15-05-2016 13:55",dtF1);
    System.out.println(ldp1 + "\n" + ldp2);

    DateTimeFormatter dtF2 = DateTimeFormatter.ofPattern("EEE d, MMMM, yyyy HH:mm");
    DateTimeFormatter dtF3 = DateTimeFormatter.ISO_LOCAL_DATE_TIME;
    LocalDateTime ldtf1 = LocalDateTime.now();
    System.out.println(ldtf1.format(dtF2) +"\n"+ldtf1.format(dtF3))

Date转换成字符串

Date today = new Date();
SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MMM-yy");
System.out.println(dateFormat.format(today)); 

dateFormat.applyPattern("dd-MM-yyyy");
System.out.println(dateFormat.format(today));
dateFormat.applyPattern("dd-MM-yyyy HH:mm:ss E");
System.out.println(dateFormat.format(today));

字符串转换成Date

第一种
    Date date = null;
    SimpleDateFormat objDf = new SimpleDateFormat(dateFormat);
    date = objDf.parse(StringDate);

第二种
    DateFormat dateFormat = DateFormat.getDateInstance(DateFormat.SHORT, Locale.US);
    String dateStr = "02/25/2016";
    Date date = dateFormat.parse(dateStr);
    System.out.println(date.getYear()); 

    SHORT 6/30/09 30/06/09
    MEDIUM Jun 30, 2009 30 juin 2009
    LONG June 30, 2009 30 juin 2009
    FULL Tuesday, June 30, 2009 mardi 30 juin 2009

比较日期大小

Boolean.valueOf(today.before(afterday)));
Boolean.valueOf(today.after(afterday)));
Boolean.valueOf(today.equals(afterday)));
Boolean.valueOf(today.isBefore(afterday)));
Boolean.valueOf(today.isAfter(afterday)));
Integer.valueOf(today.compareTo(afterday)));
Boolean.valueOf(today.isEqual(afterday)));

时区

System.out.println(TimeZone.getDefault().getDisplayName());
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
System.out.println(sdf.format(date));

sdf.setTimeZone(TimeZone.getTimeZone("Europe/London"));
System.out.println(sdf.format(date));

Calendar

Calendar calendar = Calendar.getInstance();
Calendar gregorianCalendar = new GregorianCalendar(); // 创建实例
Calendar gregorianCalendarAtSpecificDay = new GregorianCalendar(2016, Calendar.JANUARY, 1);
Calendar gregorianCalendarAtSpecificDayAndTime = new GregorianCalendar(2016, Calendar.JANUARY, 1,6, 55, 10);

calendar.add(Calendar.MONTH, -6); // 增
calendar.roll(Calendar.MONTH, -6); // 减

Calendar cal = Calendar.getInstance();
cal.setTime(new Date());
if (cal.get(Calendar.AM_PM) == Calendar.PM) System.out.println("It is PM");