JAVA 打印指定月份日历

package learnExercise;

import java.util.Scanner;

public class PrintCalender {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner input=new Scanner(System.in);
        
        System.out.print("Enter full year (e.g.,2001): ");
        int year=input.nextInt();
        
        System.out.print("Enter month as number between 1 and 12: ");
        int month=input.nextInt();
        
        printMonth(year,month);

    }

    private static void printMonth(int year, int month) {
        // TODO Auto-generated method stub
        printMonthTitle(year, month);
        printMonthBody(year, month);
    }
    
    public static void printMonthTitle(int year, int month){
        System.out.println("        "+getMonthName(month)+" "+year);
        System.out.println("-------------------------");
        System.out.println(" Sun Mont Tue Wed Thu Fri Sat");
        
    }
    
    //打印月份主体
    public static void printMonthBody(int year,int month){
        int startDay=getStartDay(year, month);
        int numberOfDaysInMonth=getNumberOfDaysInMonth(year, month);
        for(int i=0;i<startDay;i++)
            System.out.print("    ");
        for(int i=1;i<=numberOfDaysInMonth;i++){
            System.out.printf("%4d",i);
            if((i+startDay)%7==0)
                System.out.println();
        }
        System.out.println();
    }
    
    public static String getMonthName(int month){
        String  monthName="";
        switch(month){
        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="October";break;
        case 11: monthName="Nobember";break;
        case 12: monthName="December";break;
        }
        return monthName;
    }
    //获取指定月份的第一天是周几
    public static  int getStartDay(int year, int month){
        final int START_DAY_FOR_JAN_1_1800=8;
        int totalNumberOfDays=getTotalNumberOfDays(year,month);
        
        return (totalNumberOfDays+START_DAY_FOR_JAN_1_1800)%7;
    }
    //返回总共的天数，从1800年1月1日开始计算,直到指定月份1日的前一天
    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;
    }
    
    //返回指定月份的天数
    public static int getNumberOfDaysInMonth(int year,int month){
        int result=0;
        switch (month){
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:
            result=31;
            break;
        case 4:
        case 6:
        case 9:
        case 11:
            result=30;
            break;
        case 2:
            result=isLeapYear(year)?29:28;
            break;
        }
        return result;
    }
    
    //判断是否为闰年
    public static boolean isLeapYear(int year){
        return (year%400==0)||(year%4==0&&year%100!=0);
    }

}

方法抽象将程序模块化为整齐、层次分明的形式。将程序由简洁的方法构成的集合，比其他方式更容易编写、调试、维护和修改。

编写大型程序时，可以使用自顶向下或自底向上的方法，不要一次性地编写整个程序。