Java實現打印本月日曆

package com.chapter4;

import java.text.DateFormatSymbols;
import java.util.Calendar;
import java.util.GregorianCalendar;

/**
 * @date 2020-06-07
 * @author macm
 * @version 1.1
 * @purpose print Calendar
 */
public class CalendarTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		GregorianCalendar date = new GregorianCalendar();
		int today = date.get(Calendar.DAY_OF_MONTH);//獲取此時的日
		int month = date.get(Calendar.MONTH);//獲取此時的月
		
		date.set(Calendar.DAY_OF_MONTH, 1);//設置date爲本月第一天
		int weekDay = date.get(Calendar.DAY_OF_WEEK);//得到今天是周幾

		int firstDayOfWeek = date.getFirstDayOfWeek();//獲取本週的第一天(Sunday in the U.S.)
		
		/**
		 * 確定縮進距離
		 * 將日曆對象的日-1，直到一個星期的第一天爲止
		 */
		int indent = 0;
		while(weekDay != firstDayOfWeek) {
			indent++;
			date.add(Calendar.DAY_OF_MONTH, -1);
			weekDay = date.get(Calendar.DAY_OF_WEEK);
		}
		
		String [] weekDayNames = new DateFormatSymbols().getShortWeekdays();//表示星期幾的縮寫字符串
		/**
		 * 循環打印標題
		 */
		do{
			System.out.printf("%4s", weekDayNames[weekDay]);
			date.add(Calendar.DAY_OF_MONTH, 1);
			weekDay = date.get(Calendar.DAY_OF_WEEK);
		}
		while(weekDay != firstDayOfWeek);
		System.out.println();
		
		for (int i = 1; i <= indent; i++) {
			System.out.print("            ");
		}
		
		date.set(Calendar.DAY_OF_MONTH, 1);
		do {
			int day = date.get(Calendar.DAY_OF_MONTH);
			
			System.out.printf("%4d", day);
			if(day == today) {
				System.out.print("*");
			}
			else if(weekDay != 7) {
				System.out.print(" ");
			}
			
			if(day < 10 && day != today) {
				System.out.print(" ");
			}
			System.out.print("     ");
			
			date.add(Calendar.DAY_OF_MONTH, 1);
			weekDay = date.get(Calendar.DAY_OF_WEEK);
			if(weekDay == firstDayOfWeek) {
				System.out.println();
			}
		}
		while (date.get(Calendar.MONTH) == month);//直到date是下個月的第一天停止循環退出
		
		if(weekDay != firstDayOfWeek) {
			System.out.println();
		}
	}

}

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