JAVA - void 和 boolean 方法有什么区别？
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JAVA - what is the difference between void and boolean methods?
提问by moster67
I am completely new to JAVA. I am writing a wrapper-library in JAVA to make some functions available in Basic-like language.
我对 JAVA 完全陌生。我正在用 JAVA 编写一个包装库，以便在类似 Basic 的语言中提供一些功能。
I got stock at a certain point when I noted that some code were not executed in the JAVA-library although the compiler did not complain (using Eclipse). I resolved it finally by replacing the code as follows:
当我注意到一些代码没有在 JAVA 库中执行时，我在某个时候得到了库存，尽管编译器没有抱怨（使用 Eclipse）。我最终通过替换代码解决了它，如下所示：
public void VideoQuality(int vQuality) //did not work
into
进入
public boolean VideoQuality(int vQuality) //works
Here are the complete code-snippets:
以下是完整的代码片段：
public void VideoQuality(int vQuality) //did not work
{if (vQuality==16) {
vidQuality=16;
}
else if (vQuality==-16) {
vidQuality=-16;
}
else if (vQuality==0) {
vidQuality=0;
}
else
vidQuality=-16;
vitamioExt.setVideoQuality(vidQuality);
}
public boolean VideoQuality(int vQuality) //works
{if (vQuality==16) {
vidQuality=16;
}
else if (vQuality==-16) {
vidQuality=-16;
}
else if (vQuality==0) {
vidQuality=0;
}
else
vidQuality=-16;
vitamioExt.setVideoQuality(vidQuality);
return true;
}
I think voidcorresponds to a sub in Visual Basic while booleancorresponds to a function.
我认为void对应于 Visual Basic 中的 sub ，而boolean对应于一个函数。
I found it odd however that the following code worked using void
但是我发现以下代码使用void工作很奇怪
public void setVolume(float leftVolume,float rightVolume)
{
vitamioExt.setVolume(leftVolume, rightVolume);
}
I am surely missing something very obvious but I can't see why the void-code would not work while the boolean-code worked.
我肯定遗漏了一些非常明显的东西，但我不明白为什么void-code 在boolean-code 工作时不起作用。
Maybe it depends how I call the code?
也许这取决于我如何调用代码？
Anyone who can shed some lights?
谁能点亮一些灯？
EDIT: to clarify what was not working, I meant that the code:
编辑：为了澄清什么不起作用，我的意思是代码：
vitamioExt.setVideoQuality(vidQuality);
did not execute in the void-snippet.
没有在 void-snippet 中执行。
EDIT2: vidQuality was declared in a different part of the code. I just posted the snippets since the problems were with those and variables were all functioning.
EDIT2：vidQuality 是在代码的不同部分声明的。我刚刚发布了片段，因为问题出在这些片段上，并且变量都在运行。
EDIT3: At the end, I guess I must have called the void-snippet erroneously although the compiler did not compile. In either case, both snippets should execute although of course the void-snippet would be the right one to use since I did not expect a return-value.
EDIT3：最后，我想我一定是错误地调用了 void-snippet，尽管编译器没有编译。在任何一种情况下，两个片段都应该执行，尽管 void-snippet 当然是正确的使用，因为我不期望返回值。
回答by T.J. Crowder
The only difference between
之间的唯一区别
public void VideoQuality(int vQuality)
and
和
public boolean VideoQuality(int vQuality)
is that the former doesn't return a value, and the latter does (specifically, a booleanvalue). That's the full extent of the difference.
是前者不返回值，而后者返回值（特别是boolean值）。这就是差异的全部范围。
That means, for instance, that with the voidversion of VideoQuality:
这意味着，例如，void版本为VideoQuality：
boolean x = VideoQuality(10); // Will not compile
VideoQuality(10); // Will compile
...because you can't assign the result of a voidfunction to a variable.
...因为您不能将void函数的结果分配给变量。
If you used the booleanversion of VideoQuality:
如果您使用以下boolean版本VideoQuality：
boolean x = VideoQuality(10); // Will compile
VideoQuality(10); // Will compile
...because although you canassign the result of a function that returns booleanto a booleanvariable, you don't haveto. You can ignore the return value if you like. (Usually that's not good practice, but sometimes it's okay.)
......因为尽管你可以指定一个函数，返回的结果boolean的boolean变量，你不具备对。如果您愿意，可以忽略返回值。（通常这不是好的做法，但有时也可以。）
I think void corresponds to a sub in Visual Basic while boolean corresponds to a function.
我认为 void 对应于 Visual Basic 中的 sub ，而 boolean 对应于一个函数。
Loosely speaking, yes. voidindicates that the function has no return value, like Subin VB. Anything else (boolean, int, Foo, whatever) indicates that A) The function has a return value, and B) It is of the given type. So that's like Functionin VB.
粗略地说，是的。void表示该函数没有返回值，就像Sub在 VB 中一样。任何其他 ( boolean, int, Foo, 无论如何) 表示 A) 该函数有一个返回值，并且 B) 它是给定的类型。这就像Function在 VB 中一样。
回答by ICoffeeConsumer
Functions are declared with a type, much like regular variables, but a function's declared type is called its return type, which says "this function will return as a boolean when called." For example:
函数是用类型声明的，很像常规变量，但函数的声明类型称为它的返回类型，它表示“此函数在调用时将作为布尔值返回”。例如：
boolean alive = true;
boolean isDogAlive() {
return alive;
}
If this function is called, it will return true, so you could say
如果调用此函数，它将返回 true，因此您可以说
if (! isDogAlive()) { // if it returns false
System.out.println("Oh no!");
} else {
System.out.println("Yay!");
}
Functions are declared voidif they don't return anything. You shouldn't need to give a method a boolean return type unless you actually need to get the true/false value. Void should work fine for your situation.
如果函数不返回任何内容，则函数被声明为void。除非您确实需要获取真/假值，否则您不需要为方法提供布尔返回类型。Void 应该适合您的情况。
