Calendar 類是一個抽象類,爲我們提供了關於日期計算的相關功能,比如:年、月、日、時、分、秒的展示和計算。
GregorianCalendar 是 Calendar 的一個具體子類,提供了世界上大多數國家/地區使用的標準日曆系統。
菜鳥雷區
注意月份的表示,一月是0,二月是1,以此類推,12月是11。 因爲大多數人習慣於使用單詞而不是使用數字來表示月份,這樣程序也許更易讀,父類Calendar使用常量來表示月份:JANUARY、FEBRUARY等等。
示例1:GregorianCalendar類和Calendar類的使用
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
/**
* 測試日期類的使用
*
*/
public class Test {
public static void main(String[] args) {
//獲得日期的相關元素
Calendar calendar = new GregorianCalendar(2999,10,9,22,10,50); //年、月、日、時、分、秒
System.out.println(calendar);
int year = calendar.get(calendar.YEAR); //獲取年份
System.out.println(year);
int month = calendar.get(calendar.MONTH); //獲取月份
System.out.println(month); //0-11表示月份。0代表1月,1代表2月,2代表3月,,,11代表12月
int weekday = calendar.get(calendar.DAY_OF_WEEK); //星期幾,1是星期日,2是星期一,,,7是星期六
System.out.println(weekday);
int day = calendar.get(calendar.DATE); //幾號,也可以使用:DAY_OF_MONTH
System.out.println(day);
//設置日期的相關元素
Calendar c2 = new GregorianCalendar();
System.out.println(c2);
c2.set(Calendar.YEAR, 8012); //設置年份
//日期的計算
Calendar c3 = new GregorianCalendar();
c3.add(Calendar.YEAR, -100); //往前100年
System.out.println(c3);
//日期對象和時間對象的轉換
Date d4 = c3.getTime();
Calendar c4 = new GregorianCalendar();
c4.setTime(new Date());
printCalerdar(c4);
}
public static void printCalerdar(Calendar c) {
//從1983年10月10日,11:23:45 週三
int year = c.get(Calendar.YEAR);
int month = c.get(Calendar.MONTH) + 1; //0-11
int date = c.get(Calendar.DAY_OF_MONTH); //幾號
int dayweek = c.get(Calendar.DAY_OF_WEEK)-1; //1-7,1週日,2週一,3週二,,,
String dayweek2 = dayweek == 0 ?"日":"dayweek" + "";
//時分秒
int hour = c.get(Calendar.HOUR);
int minute = c.get(Calendar.MINUTE);
int second = c.get(Calendar.SECOND);
System.out.println(year + "年" + month + "月" + date + "日 " + hour + "時" + minute + "分" + second + "秒" + "周" + dayweek);
}
}
運行結果:
示例2:GregorianCalendar類和Calendar類的使用
import java.util.*;
public class TestCalendar {
public static void main(String[] args) {
// 得到相關日期元素
GregorianCalendar calendar = new GregorianCalendar(2999, 10, 9, 22, 10, 50);
int year = calendar.get(Calendar.YEAR); // 打印:1999
int month = calendar.get(Calendar.MONTH); // 打印:10
int day = calendar.get(Calendar.DAY_OF_MONTH); // 打印:9
int day2 = calendar.get(Calendar.DATE); // 打印:9
// 日:Calendar.DATE和Calendar.DAY_OF_MONTH同義
int date = calendar.get(Calendar.DAY_OF_WEEK); // 打印:3
// 星期幾 這裏是:1-7.週日是1,週一是2,。。。週六是7
System.out.println(year);
System.out.println(month);
System.out.println(day);
System.out.println(day2);
System.out.println(date);
// 設置日期
GregorianCalendar calendar2 = new GregorianCalendar();
calendar2.set(Calendar.YEAR, 2999);
calendar2.set(Calendar.MONTH, Calendar.FEBRUARY); // 月份數:0-11
calendar2.set(Calendar.DATE, 3);
calendar2.set(Calendar.HOUR_OF_DAY, 10);
calendar2.set(Calendar.MINUTE, 20);
calendar2.set(Calendar.SECOND, 23);
printCalendar(calendar2);
// 日期計算
GregorianCalendar calendar3 = new GregorianCalendar(2999, 10, 9, 22, 10, 50);
calendar3.add(Calendar.MONTH, -7); // 月份減7
calendar3.add(Calendar.DATE, 7); // 增加7天
printCalendar(calendar3);
// 日曆對象和時間對象轉化
Date d = calendar3.getTime();
GregorianCalendar calendar4 = new GregorianCalendar();
calendar4.setTime(new Date());
long g = System.currentTimeMillis();
}
static void printCalendar(Calendar calendar) {
int year = calendar.get(Calendar.YEAR);
int month = calendar.get(Calendar.MONTH) + 1;
int day = calendar.get(Calendar.DAY_OF_MONTH);
int date = calendar.get(Calendar.DAY_OF_WEEK) - 1; // 星期幾
String week = "" + ((date == 0) ? "日" : date);
int hour = calendar.get(Calendar.HOUR);
int minute = calendar.get(Calendar.MINUTE);
int second = calendar.get(Calendar.SECOND);
System.out.printf("%d年%d月%d日,星期%s %d:%d:%d\n", year, month, day,
week, hour, minute, second);
}
}
運行結果:
實例:
編寫程序,利用GregorianCalendar類,打印當前月份的日曆,如今天的日期是 2017-05-18 ,如下圖所示爲日期所在月的日曆:
代碼:
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Scanner;
/**
* 可視化日曆程序(第二個版本:完善)
*
*/
public class Test {
public static void main(String[] args) throws ParseException {
//時間字符串
//String str = "2020-7-18";
//通過鍵盤獲得時間信息
System.out.println("請輸入日期(格式:2020-10-22):");
//獲得鍵盤的輸入
Scanner scanner = new Scanner(System.in);
//拿到字符串
String str = scanner.nextLine();
//格式化時間字符串
DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
//傳值,獲得時間對象
Date date = df.parse(str);
//將拿到的日期字符串轉換爲日期類
Calendar c = new GregorianCalendar();
c.setTime(date);
//把這一天存儲在day裏
int day = c.get(Calendar.DAY_OF_MONTH);
//每月最大天數
int days = c.getActualMaximum(Calendar.DATE);
//打印日期
System.out.println("日\t一\t二\t三\t四\t五\t六");
//把當前日期置爲一
c.set(Calendar.DAY_OF_MONTH, 1);
for (int i = 0; i < c.get(Calendar.DAY_OF_WEEK) - 1; i++) {
System.out.print("\t");
}
for (int i = 1; i<= days ; i++) {
if (day == c.get(Calendar.DAY_OF_MONTH)) {
System.out.print(c.get(Calendar.DAY_OF_MONTH) + "*\t");
}else {
System.out.print(c.get(Calendar.DAY_OF_MONTH) + "\t");
}
//到了週六換行
if (c.get(Calendar.DAY_OF_WEEK) == Calendar.SATURDAY) {
System.out.println(); //換行
}
//每打完一次日期加1
c.add(Calendar.DAY_OF_MONTH, 1);
}
}
}
運行結果:
注:可通過鍵盤輸入日期,星標標註日期
教學示例:(有時間自己再敲這個)
import java.text.ParseException;
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.Scanner;
public class TestCalendar2 {
public static void main(String[] args) throws ParseException {
System.out.println("請輸入日期(格式爲:2010-3-3):");
Scanner scanner = new Scanner(System.in);
String dateString = scanner.nextLine(); // 2010-3-1
// 將輸入的字符串轉化成日期類
System.out.println("您剛剛輸入的日期是:" + dateString);
String[] str = dateString.split("-");
int year = Integer.parseInt(str[0]);
int month = new Integer(str[1]);
int day = new Integer(str[2]);
Calendar c = new GregorianCalendar(year, month - 1, day); // Month:0-11
// 大家自己補充另一種方式:將字符串通過SImpleDateFormat轉化成Date對象,
//再將Date對象轉化成日期類
// SimpleDateFormat sdfDateFormat = new SimpleDateFormat("yyyy-MM-dd");
// Date date = sdfDateFormat.parse(dateString);
// Calendar c = new GregorianCalendar();
// c.setTime(date);
// int day = c.get(Calendar.DATE);
c.set(Calendar.DATE, 1);
int dow = c.get(Calendar.DAY_OF_WEEK); // week:1-7 日一二三四五六
System.out.println("日\t一\t二\t三\t四\t五\t六");
for (int i = 0; i < dow - 1; i++) {
System.out.print("\t");
}
int maxDate = c.getActualMaximum(Calendar.DATE);
// System.out.println("maxDate:"+maxDate);
for (int i = 1; i <= maxDate; i++) {
StringBuilder sBuilder = new StringBuilder();
if (c.get(Calendar.DATE) == day) {
sBuilder.append(c.get(Calendar.DATE) + "*\t");
} else {
sBuilder.append(c.get(Calendar.DATE) + "\t");
}
System.out.print(sBuilder);
// System.out.print(c.get(Calendar.DATE)+
// ((c.get(Calendar.DATE)==day)?"*":"")+"\t");
if (c.get(Calendar.DAY_OF_WEEK) == Calendar.SATURDAY) {
System.out.print("\n");
}
c.add(Calendar.DATE, 1);
}
}
}