chapter 6 之日期

package chapter6;
import java.text.DateFormat;
import java.text.ParseException;
import java.util.*;

public class IOElseClass {
	
	//Date类的大多数方法已经不推荐使用了，它现在主要用作Calendar类和Format类的桥梁
	//在内部，日期和时间被存储为long类型，表示的日期是与1970.1.1之间的毫秒数（1万亿毫秒==31年8个月）
	public void dateMethod(){
		Date d1 =new Date(1000000000000L);
		System.out.println("1st "+d1.toString());//toString()方法默认已经被重写过了
		d1.setTime(d1.getTime()+3600000);//1hour=3600s
		System.out.println("2st "+d1.toString());
		Date nowDate =new Date();//无变元构造函数，返回的是当前时间
		System.out.println("3st "+nowDate.toString());
		//outPut is:
		//1st Sun Sep 09 09:46:40 GMT+08:00 2001
		//2st Sun Sep 09 10:46:40 GMT+08:00 2001
		//3st Sat May 22 11:53:55 GMT+08:00 2010
	}
	
	//Calendar类,字段按域考虑
	public void calendarMethod(){
		Date d1 =new Date();
		System.out.println(d1.toString());
		Calendar c =Calendar.getInstance();
		c.setTime(d1);//Calendar.SUNDAY，返回的是int值==1
		if(Calendar.SUNDAY == c.getFirstDayOfWeek()){//如果是美国的星期制
			System.out.println("Sunday is the first day of the week");
		}
		System.out.println("the day of week is "+c.get(Calendar.DAY_OF_WEEK));//星期几其实是一周的第几天
		System.out.println(c.get(Calendar.YEAR)+" "+c.get(Calendar.MONTH)+" "+c.get(Calendar.DATE));//月份的起始值是0
		c.add(Calendar.MONTH, 1);//前面是域，后面是值
		System.out.println(c.get(Calendar.YEAR)+" "+c.get(Calendar.MONTH)+" "+c.get(Calendar.DATE));
		Date d2 =c.getTime();//返回已被修改的Date对象
		System.out.println(d2.toString());
		//略roll方法，增加的数，不会递增。(exp：增加月数超12了，不会对年数产生增加)
		//outPut is:
		//Sat May 22 12:28:49 GMT+08:00 2010
		//Sunday is the first day of the week
		//the day of week is 7
		//2010 4 22
		//2010 5 22
		//Tue Jun 22 12:28:49 GMT+08:00 2010
	}
	
	//DateFormat类，格式化日期
	public void dateformatMethod(){//DateFormat在java.text包里
		Date d1 =new Date();
		System.out.println("d1 ="+d1.toString());
		DateFormat df =DateFormat.getDateInstance(DateFormat.SHORT);//如果需要记住时间，要调用getDateTimeInstance()
		String s=df.format(d1);
		System.out.println("s ="+s.toString());
		
		try {
			Date d2 =df.parse(s);
			System.out.println("d2 ="+d2.toString());
		} catch (ParseException e) {
			e.printStackTrace();
		}
		//outPut is:
		//d1 =Sat May 29 20:24:14 GMT+08:00 2010
		//s =10-5-29
		//d2 =Sat May 29 00:00:00 GMT+08:00 2010
	}
	//略Locale和NumberFormat
	
	public static void main(String[] args) {
		IOElseClass iec =new IOElseClass();
		//iec.dateMethod();
		//iec.calendarMethod();
		//iec.dateformatMethod();
	}
}