[java] 可视化日历的实现（基于Calendar类 ）

写在前面

博文安排顺序如下

1.写在前面

2.源码

3.思路

4.相关知识

该小程序是对Date类及其相关类的复习

要求如下图：实现可视化日历

实现思路

1.先从键盘输入指定格式的字符串(str)
2.将字符串用格式转换类转换成日期( Date date = format.parse(str) )
3.将日期设置成日历类( calendar.setTime(date) )
4.获取当月第一天是周几( calendar.get(Calendar.DAY_OF_WEEK) )
5.获取当月多少天( calendar.getActualMaximum(Calendar.DATE) )
6.按格式输出

源码

package TestCalendar;

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


public class visonCalendar {
    public static void main(String args[]){

        String temp = "2014-11-11";
        Calendar calendar = new GregorianCalendar();
        DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        
        try {
            Date date = df.parse(temp);
            calendar.setTime(date);
            int day = calendar.get(Calendar.DATE);
            calendar.set(Calendar.DAY_OF_MONTH, 1);
            int FirstDay = calendar.get(Calendar.DAY_OF_WEEK);
            int maxDate   = calendar.getActualMaximum(Calendar.DATE);
            System.out.println(FirstDay);
            
            System.out.println("日	一	二	三	四	五	六");
            for(int i = 1; i <= maxDate; i++ ){
                if (i == day){
                    System.out.print("*");
                }
                while((FirstDay-1)>0){   //按照需要打印的格式，本月1号从第FirstDay天开始，所以前面需要（FirstDay-1）个" 	"  
                    System.out.print(" 	");
                    FirstDay--;
                }
            
            System.out.print(i+"	");
            int w = calendar.get(Calendar.DAY_OF_WEEK);
            if(w == Calendar.SATURDAY){  //每到周六换行
                System.out.print("
");
            }
            calendar.add(Calendar.DATE, 1);  //从1号开始打印，每次打印完日期加1，否则换行if判断无效
                
        }
            } catch (ParseException e) {
            e.printStackTrace();
        }
            
    }

}

相关知识

Calendar 的 month 从 0 开始，也就是全年 12 个月由 0 ~ 11 进行表示。

而 Calendar.DAY_OF_WEEK 定义和值如下：

Calendar.SUNDAY = 1
Calendar.MONDAY = 2
Calendar.TUESDAY = 3
Calendar.WEDNESDAY = 4
Calendar.THURSDAY = 5
Calendar.FRIDAY = 6
Calendar.SATURDAY = 7

SimpleDateFormat 的格式定义

Letter	Date or Time Component	Presentation	Examples
G	Era designator	Text	AD
y	Year	Year	1996; 96
Y	Week year	Year	2009; 09
M	Month in year (context sensitive)	Month	July; Jul; 07
L	Month in year (standalone form)	Month	July; Jul; 07
w	Week in year	Number	27
W	Week in month	Number	2
D	Day in year	Number	189
d	Day in month	Number	10
F	Day of week in month	Number	2
E	Day name in week	Text	Tuesday; Tue
u	Day number of week (1 = Monday, ..., 7 = Sunday)	Number	1
a	Am/pm marker	Text	PM
H	Hour in day (0-23)	Number	0
k	Hour in day (1-24)	Number	24
K	Hour in am/pm (0-11)	Number	0
h	Hour in am/pm (1-12)	Number	12
m	Minute in hour	Number	30
s	Second in minute	Number	55
S	Millisecond	Number	978
z	Time zone	General time zone	Pacific Standard Time; PST; GMT-08:00
Z	Time zone	RFC 822 time zone	-0800
X	Time zone	ISO 8601 time zone	-08; -0800; -08:00