A constructor

1, the Date ()

Construct a Date object and initialize it to reflect the current time

Date date = new Date();
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Date(long date)

Construct a Date object and initialize it based on the number of milliseconds relative to 00:00:00, January 1, 1970 GMT

Date date = new Date(290192019);
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Commonly used method

long getTime( )

Returns the number of milliseconds represented by this Date object since 00:00:00 GMT, January 1, 1970.

Date date = new Date();
System.out.println(date.getTime());
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void setTime(long time)

Set the time and date in milliseconds since 00:00:00 GMT, January 1, 1970.

String toString( )

Convert the Date object to String of the following form: dow mon DD hh:mm: SS ZZZ YYYY Where: dow is a day in a week (Sun, MON, Tue, Wed, Thu, Fri, Sat).

int compareTo(Date date)

Compares the Date object when this method is called with the specified Date. Return 0 if they are equal. The calling object returns a negative number until the specified date. The calling object returns a positive number after the specified date.

Date is

1. Use the getTime() method to get two dates (milliseconds experienced since January 1, 1970) and compare the two values.

Use methods before(), after(), and equals().

For example, the 12th of a month is earlier than the 18th new Date(99, 2, 12). Before (new Date(99, 2, 18)); Returns true.Copy the code

Use the compareTo() method, which is defined by the Comparable interface that the Date class implements.

Formatting date

SimpleDateFormat Formats the date

Date dNow = new Date(); SimpleDateFormat ft = new SimpleDateFormat ("yyyy-MM-dd hh:mm:ss"); System.out.println(ft.format(dNow));Copy the code

Printf prints the formatted date

Date Date = new Date(); CST 2012 system.out. printf(" %tc",date); CST 2012 system.out. printf(" %tc",date); Printf (" 2012-09-10 system.out. printf(" 2012-09-10 system.out. printf ",date); Printf (" month/day/year: %tD",date); System.out.printf("HH:MM:SS PM format (12 hours) : %tr",date); //HH:MM:SS PM format (12 hours) : 10:43:36 am Printf ("HH:MM:SS format (24 hour) : %tT",date); Printf ("HH:MM (24 hour) : %tR",date);Copy the code

Parse the string for time

The SimpleDateFormat class has some additional methods, especially parse(), which attempts to parse a string in the format storage of a given SimpleDateFormat object

Example: SimpleDateFormat ft = new SimpleDateFormat (" YYYY-MM-DD "); String input = "1818-11-11"; System.out.print(input + " Parses as "); Date t; t = ft.parse(input); System.out.println(t); //1818-11-11 Parses as Wed Nov 11 00:00:00 GMT 1818Copy the code

Sleep sleep

Example: system.out.println (new Date()); Thread.sleep(1000*3); System.out.println(new Date()); system.out.println (new Date());Copy the code

Time difference

Example: long start = system.currentTimemillis (); Thread.sleep(10000); long end = System.currentTimeMillis( ); long diff = end - start; System.out.println(diff);Copy the code

Calendar

Create a Calendar object that represents the current date of the system

Calendar c = Calendar.getInstance();

Create a Calendar object for a specific time

Calendar c1 = Calendar.getInstance();

c1.set(2009, 6, 12);

The set set up

Calendar c1 = calendar.getInstance (); public final void set(int year,int month,int date){... } c1.set(2009, 6, 12); Public void set(int field,int value) c1.set(calendar.date,10); c1.set(Calendar.YEAR,2008);Copy the code

Add Settings

Calendar c1 = calendar.getInstance (); c1.add(Calendar.DATE, 10); C1. add(calendar. DATE, -10); // Date minus 10 daysCopy the code