有没有办法使这个switch语句更小更专业？

wz3gfoph  于 2021-07-06  发布在  Java
关注(0)|答案(2)|浏览(377)

我正在为圣诞节制作临期日历，需要使用switch语句。我最大的困惑是，每一天都会有一个特别为那一天设计的新班级。我正在研究google和stack overflow能提供什么。我想知道有没有别的办法来压缩这个？

  1. public void onClick(View v) {
  3.             //Calculate the days between (date - 12/7/20)
  4.             LocalDate dateBefore = java.time.LocalDate.now();
  5.             LocalDate dateAfter = LocalDate.of(2020, Month.DECEMBER, 25);
  6.             int daysAway = (int) ChronoUnit.DAYS.between(dateBefore, dateAfter);
  8.             switch(daysAway){
  9.                 case 24:
  10.                     openDay1();
  11.                     break;
  12.                 case 23:
  13.                     openDay2();
  14.                     break;
  15.                 case 22:
  16.                     openDay3;
  17.                     break;
  18.                 case 21:
  19.                     openDay4;
  20.                     break;
  21.                 case 20:
  22.                     openDay5;
  23.                     break;
  24.                 case 19:
  25.                     openDay6;
  26.                     break;
  27.                 case 18:
  28.                     openDay7;
  29.                     break;
  30.                 case 17:
  31.                     openDay8;
  32.                     break;
  33.                 case 16:
  34.                     openDay9;
  35.                     break;
  36.                 case 15:
  37.                     openDay10;
  38.                     break;
  39.                 case 14:
  40.                     openDay11;
  41.                     break;
  42.                 case 13:
  43.                     openDay12;
  44.                     break;
  45.                 case 12:
  46.                     openDay13;
  47.                     break;
  48.                 case 11:
  49.                     openDay14;
  50.                     break;
  51.                 case 10:
  52.                     openDay15;
  53.                     break;
  54.                 case 9:
  55.                     openDay16;
  56.                     break;
  57.                 case 8:
  58.                     openDay17;
  59.                     break;
  60.                 case 7:
  61.                     openDay18;
  62.                     break;
  63.                 case 6:
  64.                     openDay19;
  65.                     break;
  66.                 case 5:
  67.                     openDay20;
  68.                     break;
  69.                 case 4:
  70.                     openDay21;
  71.                     break;
  72.                 case 3:
  73.                     openDay22;
  74.                     break;
  75.                 case 2:
  76.                     openDay23;
  77.                     break;
  78.                 case 1:
  79.                     openDay24;
  80.                     break;
  81.                 case 0:
  82.                     openChristmas;
  83.                     break;
  84.                 default:
  85.                     notTime.start();
  86.                     break;
  87.             }
  88.         }

我知道这是一个巨大的混乱，这就是我试图修复！我很感激你能给我的任何反馈！

Javaswitch-statement

2条答案

按热度按时间
mf98qq94

mf98qq941#

  1. if (daysAway > 0)
  2.   openDay(25-daysAway); // you haven't shown what you would do here,
  3.          //  but presumably you don't need to write 24 separate functions
  4. else
  5.   notTime.start();
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ncgqoxb0

ncgqoxb02#

使用java 14开关表达式语法：

  1. switch (daysAway) {
  2.     case 24 -> openDay1();
  3.     case 23 -> openDay2();
  4.     case 22 -> openDay3();
  5.     case 21 -> openDay4();
  6.     // ...
  7.     case 4  -> openDay21();
  8.     case 3  -> openDay22();
  9.     case 2  -> openDay23();
  10.     case 1  -> openDay24();
  11.     case 0  -> openChristmas();
  12.     default -> notTime.start();
  13. }

由于代码非常简单，只需将其折叠到一行：

  1. switch (daysAway) {
  2.     case 24: openDay1();  break;
  3.     case 23: openDay2();  break;
  4.     case 22: openDay3();  break;
  5.     case 21: openDay4();  break;
  6.     // ...
  7.     case 4:  openDay21(); break;
  8.     case 3:  openDay22(); break;
  9.     case 2:  openDay23(); break;
  10.     case 1:  openDay24(); break;
  11.     case 0:  openChristmas(); break;
  12.     default: notTime.start();
  13. }

使用java 8方法引用数组（注意顺序颠倒）：

  1. Runnable[] OPEN_METHODS = {
  2.     this::openChristmas,
  3.     this::openDay24,
  4.     this::openDay23,
  5.     this::openDay22,
  6.     this::openDay21,
  7.     // ...
  8.     this::openDay4,
  9.     this::openDay3,
  10.     this::openDay2,
  11.     this::openDay1
  12. };
  1. if (daysAway >= 0 && daysAway <= 24) {
  2.     OPEN_METHODS[daysAway].run();
  3. } else {
  4.     notTime.start();
  5. }

既然你说过“每个（daysaway）案例都会打开一个为那一天设计的新类”，那么就使用一个接口（例如。 Runnable )以及类文字数组：

  1. Class<?>[] OPEN_CLASSES = {
  2.     OpenChristmas.class,
  3.     OpenDay24.class,
  4.     OpenDay23.class,
  5.     OpenDay22.class,
  6.     OpenDay21.class,
  7.     // ...
  8.     OpenDay4.class,
  9.     OpenDay3.class,
  10.     OpenDay2.class,
  11.     OpenDay1.class
  12. };
  1. if (daysAway < 0 || daysAway > 24) {
  2.     notTime.start();
  3. } else {
  4.     Runnable clazz;
  5.     try {
  6.         clazz = (Runnable) OPEN_CLASSES[daysAway].getConstructor().newInstance();
  7.     } catch (ReflectiveOperationException e) {
  8.         throw new AssertionError("Oops: " + e, e);
  9.     }
  10.     clazz.run();
  11. }

您还可以动态地构建类名（没有数组或 switch 声明）：

  1. if (daysAway < 0 || daysAway > 24) {
  2.     notTime.start();
  3. } else {
  4.     String className = (daysAway == 0 ? "OpenChristmas" : "OpenDay" + (25 - daysAway));
  5.     Runnable clazz;
  6.     try {
  7.         clazz = (Runnable) Class.forName(className).getConstructor().newInstance();
  8.     } catch (ReflectiveOperationException e) {
  9.         throw new AssertionError("Oops: " + e, e);
  10.     }
  11.     clazz.run();
  12. }
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