This tutorial shows you how to work with java.util.Date and java.util.Calendar.
1. Java Date Examples
Few examples to work with Date APIs.
Example 1.1 – Convert Date to String.
SimpleDateFormat sdf = new SimpleDateFormat("dd/M/yyyy");
String date = sdf.format(new Date());
System.out.println(date); //15/10/2013
Example 1.2 – Convert String to Date.
SimpleDateFormat sdf = new SimpleDateFormat("dd-M-yyyy hh:mm:ss");
String dateInString = "31-08-1982 10:20:56";
Date date = sdf.parse(dateInString);
System.out.println(date); //Tue Aug 31 10:20:56 SGT 1982
P.S Refer to this – SimpleDateFormat JavaDoc for detail date and time patterns.
Example 1.3 – Get current date time
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Date date = new Date();
System.out.println(dateFormat.format(date)); //2013/10/15 16:16:39
Example 1.4 – Convert Calendar to Date
Calendar calendar = Calendar.getInstance();
Date date = calendar.getTime();
2. Java Calendar Examples
Few examples to work with Calendar APIs.
Example 2.1 – Get current date time
SimpleDateFormat sdf = new SimpleDateFormat("yyyy MMM dd HH:mm:ss");
Calendar calendar = new GregorianCalendar(2013,0,31);
System.out.println(sdf.format(calendar.getTime()));
Output
2013 Jan 31 00:00:00
Example 2.2 – Simple Calendar example
SimpleDateFormat sdf = new SimpleDateFormat("yyyy MMM dd HH:mm:ss");
Calendar calendar = new GregorianCalendar(2013,1,28,13,24,56);
int year = calendar.get(Calendar.YEAR);
int month = calendar.get(Calendar.MONTH); // Jan = 0, dec = 11
int dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH);
int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK);
int weekOfYear = calendar.get(Calendar.WEEK_OF_YEAR);
int weekOfMonth= calendar.get(Calendar.WEEK_OF_MONTH);
int hour = calendar.get(Calendar.HOUR); // 12 hour clock
int hourOfDay = calendar.get(Calendar.HOUR_OF_DAY); // 24 hour clock
int minute = calendar.get(Calendar.MINUTE);
int second = calendar.get(Calendar.SECOND);
int millisecond= calendar.get(Calendar.MILLISECOND);
System.out.println(sdf.format(calendar.getTime()));
System.out.println("year \t\t: " + year);
System.out.println("month \t\t: " + month);
System.out.println("dayOfMonth \t: " + dayOfMonth);
System.out.println("dayOfWeek \t: " + dayOfWeek);
System.out.println("weekOfYear \t: " + weekOfYear);
System.out.println("weekOfMonth \t: " + weekOfMonth);
System.out.println("hour \t\t: " + hour);
System.out.println("hourOfDay \t: " + hourOfDay);
System.out.println("minute \t\t: " + minute);
System.out.println("second \t\t: " + second);
System.out.println("millisecond \t: " + millisecond);
Output
2013 Feb 28 13:24:56
year : 2013
month : 1
dayOfMonth : 28
dayOfWeek : 5
weekOfYear : 9
weekOfMonth : 5
hour : 1
hourOfDay : 13
minute : 24
second : 56
millisecond : 0
Example 2.3 – Set a date manually.
SimpleDateFormat sdf = new SimpleDateFormat("yyyy MMM dd HH:mm:ss");
Calendar calendar = new GregorianCalendar(2013,1,28,13,24,56);
System.out.println("#1. " + sdf.format(calendar.getTime()));
//update a date
calendar.set(Calendar.YEAR, 2014);
calendar.set(Calendar.MONTH, 11);
calendar.set(Calendar.MINUTE, 33);
System.out.println("#2. " + sdf.format(calendar.getTime()));
Output
#1. 2013 Feb 28 13:24:56
#2. 2014 Dec 28 13:33:56
Example 2.4– Add or subtract from a date.
SimpleDateFormat sdf = new SimpleDateFormat("yyyy MMM dd");
Calendar calendar = new GregorianCalendar(2013,10,28);
System.out.println("Date : " + sdf.format(calendar.getTime()));
//add one month
calendar.add(Calendar.MONTH, 1);
System.out.println("Date : " + sdf.format(calendar.getTime()));
//subtract 10 days
calendar.add(Calendar.DAY_OF_MONTH, -10);
System.out.println("Date : " + sdf.format(calendar.getTime()));
Output
Date : 2013 Nov 28
Date : 2013 Dec 28
Date : 2013 Dec 18
Example 2.5– Convert Date to Calendar.
SimpleDateFormat sdf = new SimpleDateFormat("dd-M-yyyy hh:mm:ss");
String dateInString = "22-01-2015 10:20:56";
Date date = sdf.parse(dateInString);
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
https://www.mkyong.com/java/java-date-and-calendar-examples/
http://www.mkyong.com/tutorials/java-date-time-tutorials/
原文地址：https://www.cnblogs.com/shy1766IT/p/10105170.html