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  1. import java.util.ArrayList;
  2. import java.util.Collections;
  3. import java.util.List;
  4. import java.util.Scanner;
  5.  
  6. class Koyomi {
  7.     public static void main(String[] args) {
  8.         IntegerScanner intScanner = new IntegerScanner(new Scanner(System.in));
  9.         int year = intScanner.read("Year?", 2000, 2040);
  10.         int month = intScanner.read("Month?", 1, 12);
  11.         new Calendar().print(year, month);
  12.     }
  13. }
  14.  
  15. class Calendar {
  16.     public void print(int year, int month){
  17.         int monthNext, yearNext;
  18.         if(month == 12){
  19.             monthNext = 1;
  20.             yearNext = year + 1;
  21.         }else{
  22.             monthNext = month + 1;
  23.             yearNext = year;
  24.         }
  25.  
  26.         int z1 = calcZeller(year, month);
  27.         int z2 = calcZeller(yearNext, monthNext);
  28.         int lastDate = getLastDateOfMonth(z1, z2);
  29.         int pad = convertToDayOfTheWeekIndex(z1);
  30.  
  31.         System.out.printf("\n     %d年 %d月\n日 月 火 水 木 金 土\n", year, month);
  32.         List<String> list = new ArrayList<String>(Collections.nCopies(pad, "  "));
  33.         int i = pad;
  34.         for(int date = 1; date <= lastDate; date++){
  35.             list.add(String.format("%2d", date));
  36.             if(++i == 7){
  37.                 System.out.println(String.join(" ", list));
  38.                 list.clear();
  39.                 i = 0;
  40.             }
  41.         }
  42.         if(list.size() > 0){
  43.             System.out.println(String.join(" ", list));
  44.         }
  45.     }
  46.     /** ツェラーの式による曜日番号計算 (0=土曜日) */
  47.     int calcZeller(int year, int month) {
  48.         if (month <= 2) {
  49.             month += 12;
  50.             year -= 1;
  51.         }
  52.         int j = year / 100;
  53.         int k = year % 100;
  54.         int a = (month + 1) * 26 / 10;
  55.         int z = (1 + a + k + k / 4 + j / 4 - 2 * j) % 7;
  56.         if(z < 0) {
  57.             z += 7;
  58.         }
  59.         return z;
  60.     }
  61.     /** ツェラーの計算結果を曜日インデックス(0=日曜)に変換 */
  62.     int convertToDayOfTheWeekIndex(int zeller) {
  63.         return zeller == 0 ? 6 : zeller - 1;
  64.     }
  65.     /** 対象月初日と翌月初日の曜日のギャップから月の最終日(日数)を計算 */
  66.     int getLastDateOfMonth(int zeller1, int zeller2){
  67.         int gap = zeller2 - zeller1;
  68.         if(gap < 0){
  69.             gap += 7;
  70.         }
  71.         return 28 + gap;
  72.     }
  73. }
  74.  
  75. class IntegerScanner {
  76.     private Scanner scanner;
  77.     public IntegerScanner(Scanner scanner) {
  78.         this.scanner = scanner;
  79.     }
  80.     public int read(String message, int min, int max) {
  81.         while (true) {
  82.             System.out.printf("%s [%d-%d] > ", message, min, max);
  83.             String line = this.scanner.nextLine();
  84.             try {
  85.                 int n = Integer.parseInt(line);
  86.                 if (min <= n && n <= max) {
  87.                     return n;
  88.                 } else {
  89.                     System.out.println("範囲外です");
  90.                 }
  91.             } catch (NumberFormatException e) {
  92.                 System.out.println("正しい入力ではありません。");
  93.             }
  94.         }
  95.     }
  96. }
  97.  
Success #stdin #stdout 0.12s 29520KB
comments (?)
stdin
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100000
a
2018
6
stdout
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Year? [2000-2040] > 範囲外です
Year? [2000-2040] > 正しい入力ではありません。
Year? [2000-2040] > Month? [1-12] > 
     2018年 6月
日 月 火 水 木 金 土
                1  2
 3  4  5  6  7  8  9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
https://ideone.com/WWnU6F
language:
Java (12.0.1)
created:
5 years ago
visibility:
public

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