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。