カレンダーの印刷

このアルゴリズムはカレンダーを印刷するので、多くの友达にとって少し难しいかもしれませんが、笔者はやはりみんなに无理をして読み终わらせたいと思っています.结局、このアルゴリズムをマスターしたら、友达はカレンダーを买う必要はありません~~~よし、コードを见てみましょう

package printdate;

import java.util.Scanner;

/**
 *       ，         。
 *
 * Created by     on 2017/6/1.
 */
public class PrintCalendar {
    public static void main(String[] args){
        Scanner input = new Scanner(System.in);
        //    
        System.out.println("please enter full year(eg.2000)");
        int year = input.nextInt();

        //    
        System.out.println("enter mouth between 1 and 12");
        int month = input.nextInt();

        //    ，    
        printCalender(year,month);
    }

    /**
     *            
     * @param year   
     * @param month   
     */
    public static void printCalender(int year,int month){
        //       
        printTitle(year,month);

        //         
        printBody(year,month);

    }

    /**
     *        
     * @param year
     * @param month
     */
    public static void printTitle(int year, int month){
        System.out.println("         " + getMonth(month) + "  " + year);
        System.out.println("-------------------------------");
        System.out.println("  Sun   Mon  Tue   Wed  Thu  Fri Sat ");

    }

    /**
     *          
     * @param mouth
     * @return
     */
    public static String getMonth(int mouth){
        String monthName = " ";
        switch (mouth){
            case 1:
                monthName = "January"; break;
            case 2:
                monthName = "February";break;
            case 3:
                monthName = "March";break;
            case 4:
                monthName = "April";break;
            case 5:
                monthName = "May";break;
            case 6:
                monthName = "June";break;
            case 7:
                monthName = "July";break;
            case 8:
                monthName = "August";break;
            case 9:
                monthName = "September";break;
            case 10:
                monthName = "Octomber";break;
            case 11:
                monthName = "November";break;
            case 12:
                monthName = "December";
        }
        return monthName;
    }

    /**
     *          
     * @param year
     * @param month
     */
    public static void printBody(int year,int month){
        //            
        int startDay = getStartDays(year,month);
        //         
        int numberOfDaysInMonth = getNumberOfDaysInMonth(year,month);

        //               
        int i ;
        for( i = 0; i < startDay; i++) {
            System.out.print("     ");
        }

        for( i = 1; i <= numberOfDaysInMonth; i++){
            System.out.printf("%5d",i);
            //      
            if((i + startDay) % 7 == 0){
                System.out.println();
            }

        }

    }


    /**
     *          
     * @param year
     * @param month
     */
    public static  int getStartDays(int year, int month){
        // 1800 1 1          
        final int START_DAY_FOR_JAN_1_1800 = 3;
        //                 
        int totalNumberOfDays = getTotalNumberOfDays(year,month);
        //       
        return (totalNumberOfDays + START_DAY_FOR_JAN_1_1800) % 7;

    }

    /**
     *             
     * @param year
     * @param month
     * @return
     */
    public static int getTotalNumberOfDays(int year,int month){
        int total = 0;

        //               
        for(int i = 1800; i < year; i++){
            //       
            if(isLeapYear(i)){
                total = total + 366;
            }
            else {
                total = total + 365;
            }
        }

        //                
        for(int i = 1; i < month; i++){
            total = total + getNumberOfDaysInMonth(year,i);
        }

        return total;
    }

    /**
     *        
     * @param year
     * @param month
     * @return
     */
    public static int getNumberOfDaysInMonth(int year,int month){
        if(month == 1 || month == 3 || month == 5 || month == 7 || month == 7 || month == 8 || month == 10 || month == 13 ){
            return  31;
        }
        if(month == 4 || month == 6 || month == 9 || month == 9 || month == 11){
            return  30;
        }
        if(month == 2){
            return  isLeapYear(year) ? 29 : 28;
        }

        return  0;
    }

    public static boolean isLeapYear(int year){
        return year % 400 == 0 || (year % 4 == 0 && year % 100 != 0);
    }


}