switch case 语句中的布尔逻辑 - Java
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Boolean logic in switch case statement - Java
提问by Hyman
switch (i) {
case ("+" || "/"):
setOperator("i");
break;
}
What is the best way to do this in Java?
在 Java 中执行此操作的最佳方法是什么？
回答by Alex K
Of course.
当然。
Just use
只需使用
if(i.equals("+") || i.equals("/")) {
setOperator("i");
}
OR if you have to use a switch statement, you can do it this way:
或者，如果您必须使用 switch 语句，您可以这样做：
switch(i) {
case "+":
case "/":
setOperator("i");
break;
}
Basically, you can't really have multiple cases the way you had thought about it. It's not the same structure as an if statement, where you can do various logical operations. Java does notgo through and do an if statement for each of the cases.
基本上，你不可能像你想象的那样有多个案例。它与 if 语句的结构不同，您可以在其中执行各种逻辑操作。Java并没有经历做一个if语句为每一个案件。
Instead, each time you have case("foo"), Java sees this as something called a Case Label. It is the reason that we sometimes opt to use switch statements, even though they are very primitive and sometimes not very convenient. Because we have case labels, the computer only has to do one evaluation, and it can jump to correct place and execute the right code.
相反，每次您拥有 时case("foo")，Java 都将其视为称为案例标签的东西。这就是我们有时选择使用 switch 语句的原因，即使它们非常原始并且有时不太方便。因为我们有 case 标签，计算机只需要做一次评估，它就可以跳转到正确的地方并执行正确的代码。
Here is a quote from a website that may help you:
这是一个网站的引用，可以帮助您：
A switch statement, as it is most often used, has the form:
最常用的 switch 语句具有以下形式：
switch (expression) {
case constant-1:
statements-1
break;
case constant-2:
statements-2
break;
.
. // (more cases)
.
case constant-N:
statements-N
break;
default: // optional default case
statements-(N+1)
} // end of switch statement
This has exactly the same effect as the following multiway if statement, but the switch statement can be more efficient because the computer can evaluate one expression and jump directly to the correct case, whereas in the if statement, the computer must evaluate up to N expressions before it knows which set of statements to execute:
这与下面的多路 if 语句效果完全相同，但 switch 语句效率更高，因为计算机可以计算一个表达式并直接跳转到正确的 case，而在 if 语句中，计算机必须计算最多 N 个表达式在它知道要执行哪组语句之前：
if (expression == constant-1) { // but use .equals for String!!
statements-2
}
else if (expression == constant-2) {
statements-3
}
else
.
.
.
else if (expression == constant-N) {
statements-N
}
else {
statements-(N+1)
}
回答by Rustam
yes you can do as: Fall throughin swith case
是的，你可以这样做：Fall through在swith case
switch (i) {
case "+":
case "/":
setOperator(i);
break;
}
回答by Abhi
switch (i) {
case ("+"):
case ("/"):
setOperator("i");
break;
}
