在 switch 中使用关系运算符

2022-01-19 00:00:00 operators switch-statement java relational

有没有办法在 switch 语句中使用关系运算符(<、<=、>、>=)?

Is there a way to use relational operators (<,<=,>,>=) in a switch statement?

int score = 95;

switch(score)  {
   case (score >= 90):
      // do stuff
}

上面的例子(显然)不起作用

the above example (obviously) doesn't work

推荐答案

不，你不能.
来自 jls-14.11 

The type of the Expression must be char, byte, short, int, Character, Byte, Short, Integer, String, or an enum type (§8.9), or a compile-time error occurs.

关系运算符 (<,<=,>,>=) 会产生 boolean，这是不允许的.

Relational operators (<,<=,>,>=) results in boolean and which is not allowded.

以下所有条件都必须为真，否则会发生编译时错误:

All of the following must be true, or a compile-time error occurs:

  • 与 switch 语句关联的每个 case 常量表达式都必须可分配(第 5.2 节)到 switch 表达式的类型.

  • Every case constant expression associated with a switch statement must be assignable (§5.2) to the type of the switch Expression.

与 switch 语句关联的两个 case 常量表达式不能具有相同的值.

No two of the case constant expressions associated with a switch statement may have the same value.

没有开关标签为空.

同一个switch语句最多可以关联一个默认标签.

At most one default label may be associated with the same switch statement.

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