如何在 Java 中使用“或”？
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How to use 'or' in Java?
提问by user2916424
I'm quite new to Java, and can't figure out how to use 'or'. What is the Java equivalent?
I've already tried &&and ||but eclipse does not recognise it.
我对 Java 很陌生，无法弄清楚如何使用“或”。Java 等价物是什么？我已经尝试过了&&，||但是 eclipse 无法识别它。
This is part of my code:
这是我的代码的一部分：
if (action.equals ("run") || ("sprint")) {
System.out.println("you ran");
}
else {
System.out.println("else");
}
回答by T.J. Crowder
I've already tried && and || but eclipse does not recognise it.
我已经尝试过 && 和 || 但 eclipse 无法识别它。
That's very strange, but just to cover the basics: Let's assume you have the variable aand it contains the value 5. Then:
这很奇怪，但只是为了涵盖基础知识：假设您有变量a并且它包含 value 5。然后：
if (a == 5 || a == 7)
...will be true, because the first part of the expression (a == 5) is true. So the statement "aequals 5 oraequals 7" is true.
...将是真的，因为表达式 ( a == 5)的第一部分是真的。所以“a等于 5或a等于 7”的说法是正确的。
The ||operator can only be used, in Java, where a boolean (true or false) expression is expected, such as in an ifstatement like the above. So pretty much in an ifor a conditional operator (that ?...:thing, sometimes called the ternary operator).
所述||操作者仅可用于在Java中，其中布尔型（真或假）表达的预期，诸如在if象上面的语句。在 an ifor 条件运算符（那个?...:东西，有时称为三元运算符）中非常多。
Re your edit, the problem is that both sides of your ||operator aren't true or false ("boolean") expressions. Your statement:
重新编辑，问题在于您的||运算符的两边都不是真或假（“布尔”）表达式。你的声明：
if (action.equals ("run") || ("sprint")){
breaks down like this:
分解如下：
if (
action.equals ("run")
|| // ("or")
("sprint")
)
the second part of that isn't a true/false, it's a string. The correct way to express that in Java (or nearly any other programming language) is:
第二部分不是真/假，它是一个字符串。在 Java（或几乎任何其他编程语言）中表达它的正确方法是：
if (action.equals ("run") || action.equals ("sprint")){
Now both sides of the ||result in true/false exprssions:
现在||结果的两边都是真/假表达式：
if (
action.equals ("run")
|| // ("or")
action.equals ("sprint")
)
The reason for this is that the second part may have nothing whatsoever to do with action, and so the compiler can't assume you mean to re-use it in the second part of the expression. You might, for instance, want to use ||with two completely unrelated things:
这样做的原因是第二部分可能与 无关action，因此编译器不能假设您打算在表达式的第二部分中重新使用它。例如，您可能想要使用||两个完全不相关的东西：
if (action.equals("run") || somethingElse.equals("run")) {
回答by Fabio Carello
Ok. ("sprint")is not a Boolean expression. Since a ifcondition expects a Boolean expression your code returns an error. You should change the line with:
好的。("sprint")不是布尔表达式。由于if条件需要布尔表达式，因此您的代码会返回错误。您应该将行更改为：
if (action.equals ("run") || action.equals("sprint")){
回答by StFS
The equalsmethod returns a boolean and the || operator wants two booleans on each side.
该equals方法返回一个布尔值和 || 操作员需要每边两个布尔值。
You're doing an action.equals("run")on one side but then a ("sprint")on the other which isn't a boolean expression.
你在action.equals("run")一侧做一个，然后在另一侧做一个("sprint")不是布尔表达式的。
Change your code like so:
像这样更改您的代码：
if (action.equals("run") || action.equals("sprint")){
if (action.equals("run") || action.equals("sprint")){
