Detailed Explanation of Date Method in Java

Introduce the column first

This column is my own journey of learning Java, pure hand-knocked code, I followed the dark horse course to learn, and added some of my own understanding, and made
appropriate modifications to the code and notes. I hope it can be helpful to everyone, and at the same time, please supervise me, give suggestions on the code I wrote, and learn from each other.
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Date method

The Date class is a class used to represent dates and times. It provides a series of methods to manipulate dates and times.

common method

1. Construction method

Date(): Creates a Date object representing the current date and time.
Date(long milliseconds): Creates a Date object based on the specified number of milliseconds.

2. How to get the date and time:

getTime(): Returns the number of milliseconds since January 1, 1970 00:00:00 GMT.

example

long milliseconds = specificDate.getTime();

getYear(): Returns the year of the current date (counting from 1900).
getMonth(): Returns the month of the current date (0 means January, 11 means December).
getDate(): Returns the number of days in the current date (1 means the first day).
getDay(): Returns the day of the week of the current date (0 means Sunday, 6 means Saturday).
getHours(): Returns the hours (0-23) of the current time.
getMinutes(): Returns the minutes (0-59) of the current time.
getSeconds(): Returns the seconds (0-59) of the current time.
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3. How to set the date and time:

setTime(long milliseconds): Set the date and time represented by the Date object.
setYear(int year): Set the year of the current date.
setMonth(int month): Set the month of the current date.
setDate(int day): Set the number of days in the current date.
setHours(int hours): Set the hours of the current time.
setMinutes(int minutes): Set the minutes of the current time.
setSeconds(int seconds): Set the seconds of the current time.
insert image description here #### 4. Other methods:
toString(): Returns the string representation of the Date object.

example

String dateString = specificDate.toString();

before(Date date): Determine whether the current date is before the specified date.

example

boolean isBefore = specificDate.before(currentDate);

after(Date date): Determine whether the current date is after the specified date.

example

boolean isAfter = specificDate.after(currentDate);```

equals(Object obj): Determine whether the current date is equal to the specified object.

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Comprehensive case

the code

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class crj {
    
    
    public static void main(String[] args) {
    
    
        //Date():
        Date d1 = new Date();
        System.out.println(d1);
        //Date(long date):  1000（毫秒）*60*60   一小时
        Date d2 = new Date(1000 * 60 * 60);
        System.out.println(d2);

        Date d = new Date();
//        SimpleDateFormat sdf = new SimpleDateFormat();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
        String s = sdf.format(d);
        System.out.println(s);
        System.out.println("-------");
        //解析
        String ss="2021-10-27 11:11:11";
//        SimpleDateFormat sdf2=new SimpleDateFormat("2021年10月27日 11:11:11");
        SimpleDateFormat sdf2=new SimpleDateFormat("2021-10-27 11:11:11");
        Date dd= null;
        try {
    
    
            dd = sdf2.parse(ss);
        } catch (ParseException e) {
    
    
            e.printStackTrace();
        }
        System.out.println(dd);
    }
}

result

Tue Aug 08 07:50:35 CST 2023
Thu Jan 01 09:00:00 CST 1970
2023年08月08日 07:50:35
-------
Thu Jan 01 00:00:00 CST 1970