“此处不允许使用‘void’类型”错误（Java）
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"'void' type not allowed here" error (Java)
提问by David
When I try to compile this:
当我尝试编译它时：
import java.awt.* ;
class obj
{
public static void printPoint (Point p)
{
System.out.println ("(" + p.x + ", " + p.y + ")");
}
public static void main (String[]arg)
{
Point blank = new Point (3,4) ;
System.out.println (printPoint (blank)) ;
}
}
I get this error:
我收到此错误：
obj.java:12: 'void' type not allowed here
System.out.println (printPoint (blank)) ;
^
1 error
I don't really know how to start asking about this other than to ask:
除了问：我真的不知道如何开始询问这个问题：
- What went wrong here?
- What does this error message mean?
- 这里出了什么问题？
- 这个错误信息是什么意思？
采纳答案by Justin Ethier
If a method returns voidthen there is nothing to print, hence this error message. Since printPoint already prints data to the console, you should just call it directly:
如果方法返回void，则没有可打印的内容，因此会出现此错误消息。由于 printPoint 已经将数据打印到控制台，您应该直接调用它：
printPoint (blank);
回答by Andrew Hare
You are trying to print the result of printPointwhich doesn't return anything. You will need to change your code to do either of these two things:
您正在尝试打印printPoint不返回任何内容的结果。您需要更改代码以执行以下两项操作之一：
class obj
{
public static void printPoint (Point p)
{
System.out.println ("(" + p.x + ", " + p.y + ")");
}
public static void main (String[]arg)
{
Point blank = new Point (3,4) ;
printPoint (blank) ;
}
}
or this:
或这个：
class obj
{
public static String printPoint (Point p)
{
return "(" + p.x + ", " + p.y + ")";
}
public static void main (String[]arg)
{
Point blank = new Point (3,4) ;
System.out.println (printPoint (blank)) ;
}
}
回答by Carl Manaster
You are passing the result of printPoint()- which is void - to the println()function.
您将printPoint()- 无效 -的结果传递给println()函数。
回答by Ben Zotto
The type problem is that printlntakes a String to print, but instead of a string, you're calling the printPointmethod which is returning void.
类型问题是println需要一个 String 来打印，但不是一个字符串，而是调用printPoint返回void.
You can just call printPoint(blank);in your main function and leave it at that.
你可以只调用printPoint(blank);你的主函数并保留它。
回答by ggf31416
printPointprints by itself rather than returning a string. To fix that call printPoint(blank) without the System.out.println.
printPoint打印本身而不是返回一个字符串。要在printPoint没有System.out.println.
A better alternative may be: make printPoint(Point p)return a string (and change its name to something like FormatPoint), that way the method may be used to format a point for the console, GUI, print, etc rather than being tied to the console.
更好的选择可能是：makeprintPoint(Point p)返回一个字符串（并将其名称更改为类似FormatPoint），这样该方法可用于格式化控制台、GUI、打印等的点，而不是绑定到控制台。
回答by fastcodejava
You probably wanted to do : printPoint (blank);. Looks like you are trying to print twice; once inside printPoint()and once inside main().
你可能想做：printPoint (blank);。看起来您正在尝试打印两次；一次进去printPoint()，一次进去main()。
