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Java 中的变量值开关案例

发布于 2024-10-17 06:16:13 字数 71 浏览 8 评论 0原文

我希望进行一个切换，其中 5 个案例在功能上相同，但还会有其他独特的案例。有没有办法列出处理 5 个不同值的 case 值？谢谢

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葬シ愛 2024-10-24 06:16:13

您可以在开关中复合标签

switch (variable) {
  case 'a': case 'b' : case 'c' : case 'd' :
     do something;
     break;
  case 'e': case 'f' :
     do something else
     break;
  default:
     do something;
}

将开关视为跳转到标签（可能与跳转（中断）到末尾相结合）会有所帮助。这意味着开关

switch (variable) {
  case 'a': case 'b' : case 'c' : case 'd' :
     do something;
     // note that there's no break here.
  case 'e': case 'f' :
     do something else
     break;
  default:
     do something;
}

将为“a”、“b”、“c”和“d”“做某事”和“做其他事”；而它只会为“e”和“f”“做其他事情”。最后，如果不是上述任何一个，它就会遇到“做某事”的默认块。

You can compound the labels in the switch

switch (variable) {
  case 'a': case 'b' : case 'c' : case 'd' :
     do something;
     break;
  case 'e': case 'f' :
     do something else
     break;
  default:
     do something;
}

Thinking of a switch as a jump to a label (possibly coupled with a jump (the break) to the end) will help. That means the switch

switch (variable) {
  case 'a': case 'b' : case 'c' : case 'd' :
     do something;
     // note that there's no break here.
  case 'e': case 'f' :
     do something else
     break;
  default:
     do something;
}

will "do something" and "do something else" for 'a', 'b', 'c', and 'd'; while it will only "do something else" for 'e' and 'f'. Finally if it's not any of the above it hits the default block of "do something".

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半步萧音过轻尘 2024-10-24 06:16:13

switch (value) {
case 1:
case 2:
case 3:
case 4:
    doSomethingIdentical();
    break;
case 5:
    doSomethingDifferent();
    break;
default:
    break;
}

switch (value) {
case 1:
case 2:
case 3:
case 4:
    doSomethingIdentical();
    break;
case 5:
    doSomethingDifferent();
    break;
default:
    break;
}

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べ映画 2024-10-24 06:16:13

这很容易做到。不要只使用一个 case 值来处理所有 5 个不同的值，而是让 5 个 case 值相互传递，如下所示：


switch(value)
{
    case 1:
    case 2:
        //case 1 and 2 will both result in this code being executed
        doSomething();
        break;
    case 3:
        doSomethingElse();
        break;
}

This is very easy to do. Instead of just having one case value that handles all 5 different values, let the 5 case values fall through to each other, like so:


switch(value)
{
    case 1:
    case 2:
        //case 1 and 2 will both result in this code being executed
        doSomething();
        break;
    case 3:
        doSomethingElse();
        break;
}

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暮年 2024-10-24 06:16:13

只要您不在开关上放置 break; ，它就会跳到下一条语句。

这样，你就可以得到这样的东西：

String value(int val) {
    String out = "";
    switch(val) {
    case 0:
        out = "case 0";
        break;
    case 1:
        out = "case 1";
        break;
    case 2:
    case 3:
    case 4:
    case 5:
    case 6:
        out = "case 2, 3, 4, 5 or 6";
        break;
    case 7:
        out = "case 7";
        break;
    }
    return out;
}

As long as you don't put a break; on a switch it will fall through to the next statement.

In that way, you can have something like this:

String value(int val) {
    String out = "";
    switch(val) {
    case 0:
        out = "case 0";
        break;
    case 1:
        out = "case 1";
        break;
    case 2:
    case 3:
    case 4:
    case 5:
    case 6:
        out = "case 2, 3, 4, 5 or 6";
        break;
    case 7:
        out = "case 7";
        break;
    }
    return out;
}

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ζ澈沫 2024-10-24 06:16:13

是的，只需使用这样的开关：

switch(v) {

   case 1:
   case 2:
   case 3:
       identicFunctionality();
       break;
   case 4:
       other01();
       break;
   case 5:
       other02();
       break;
   default:
       _default();
}

Yes, just use a switch like this:

switch(v) {

   case 1:
   case 2:
   case 3:
       identicFunctionality();
       break;
   case 4:
       other01();
       break;
   case 5:
       other02();
       break;
   default:
       _default();
}

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苏大泽ㄣ 2024-10-24 06:16:13

从 Java 12 开始，我相信它是受支持的。查看 JEP 354。我从未使用过该语法，但我认为对于您的情况，它会像这样运行。

switch (day) {
    case 1, 2, 3, 4, 5    -> System.out.println("1-5");
    case 7                -> System.out.println(7);
    case 8                -> System.out.println(8);
    case 9                -> System.out.println(9);
}