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  • Java Date and Calendar examples

    Java Date and Calendar examples

    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 : " + year);
    System.out.println("month : " + month);
    System.out.println("dayOfMonth : " + dayOfMonth);
    System.out.println("dayOfWeek : " + dayOfWeek);
    System.out.println("weekOfYear : " + weekOfYear);
    System.out.println("weekOfMonth : " + weekOfMonth);

    System.out.println("hour : " + hour);
    System.out.println("hourOfDay : " + hourOfDay);
    System.out.println("minute : " + minute);
    System.out.println("second : " + second);
    System.out.println("millisecond : " + 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/

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  • 原文地址:https://www.cnblogs.com/shy1766IT/p/10105170.html
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