java语言基础--日期类

Date类

Date d1 = new Date();　　//d1 ----   Fri Aug 17 20:45:23 CST 2018

Date d2 = new Date(0);    //d2  ----   Thu Jan 01 08:00:00 CST 1970

SimpleDateFormat类

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss SSS");
String date = sdf.format(d1);　　　　//date  ----   2018-08-17 08:52:32 887

将字符创转化成日期

String s  ="2017-1-1 8:00:00";
SimpleDateFormat d = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
try {
    Date da = d.parse(s);
    System.out.println(d.format(da));
} catch (ParseException e) {
    e.printStackTrace();
}

Calendar类

抽象类；

Calendar c = Calendar.getInstance();
int i =c.get(Calendar.DAY_OF_MONTH );
System.out.println(i);
int w =c.get(Calendar.DAY_OF_WEEK);
System.out.println(w);     //从上周日开始数

计算2008-8-8星期几：

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

public class Main {

    public static void main(String[] args) {
        String s = "2008-8-8";
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Date date =null;
        try {
            date = sdf.parse(s);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        
        System.out.println(c.get(Calendar.DAY_OF_WEEK));
    }
}

计算我们来到世界多长时间了

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

public class Main2 {

    public static void  main(String[] args) throws ParseException {
        Date d  = new Date();
        String s = "1994-03-05";
        
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        
        Date date = sdf.parse(s);
        
        long now = d.getTime();
        long birthday = date.getTime();
        
        long  time = now - birthday;
        System.out.println(time/1000/60/60/24);
    }
}