我并不是 100% 相信这是一个好主意，但我今天遇到了一些代码，目前的实现如下：
class MyWidget <T extends Enum<T> > {
MyWidget(Map<T, Integer> valueMap) {
mValueMap = valueMap;
}
Map<T, Integer> mValueMap;
}
其中 MyWidget then 提供了使用 mValueMap 进行转换的方法传入的 Enum 与 Integer 之间的传入。
我正在考虑做的是尝试重构它，以便我声明我的枚举：
interface MyInterface {
public Integer getValue();
}
enum MyEnum implements MyInterface {
foo, bar;
public Integer getValue() {
return ordinal();
}
}
然后我就能够将 MyWidget 重写为看起来模糊的东西：
public class MyWidget<T extends Enum<T> extends MyInterface> {
...
}
然后就能够从 MyInterface 对 MyWidget 内的 T 类型对象调用 getValue() 方法。 当然，问题在于“ extends MyInterface>”不是有效的语法。 有什么办法可以解决这个问题吗？
我不想只拥有 MyWidget，因为 T 是一个枚举也很重要。
提前致谢！
I'm not 100% convinced that this is a good idea, but I bumped into some code today that's currently implemented as:
class MyWidget <T extends Enum<T> > {
MyWidget(Map<T, Integer> valueMap) {
mValueMap = valueMap;
}
Map<T, Integer> mValueMap;
}
where MyWidget then offers methods that use mValueMap to convert the passed-in Enum to/from an Integer.
What I was considering doing was trying to refactor this, so that I'd declare my enumeration:
interface MyInterface {
public Integer getValue();
}
enum MyEnum implements MyInterface {
foo, bar;
public Integer getValue() {
return ordinal();
}
}
And I'd then be able to rewrite MyWidget into something that looked vaguely like this:
public class MyWidget<T extends Enum<T> extends MyInterface> {
...
}
and would then be able to call the getValue() method from MyInterface on T-type objects within MyWidget. The problem, of course, is that "<T extends Enum<T> extends MyInterface>" isn't valid syntax. Is there any way to pull this off?
I don't want to just have MyWidget<T extends MyInterface>, because it's also important that T be an enumeration.
Thanks in advance!
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使用“
&”代替：JLS 将此称为“交叉类型”，但我在 Java 教程中找不到任何提及。 我只想说它完全符合您希望“
extends”所做的事情。另外，我应该提到的是，您可以在交叉类型中拥有任意多种类型。 因此，如果您愿意，您可以这样做：
[注意：此代码示例不应被解释为对
Cloneable接口的认可； 当时只是方便而已。]Use an '
&' instead:The JLS calls this an "intersection type", but I can find no mention of it in the Java tutorials. I'll just say that it does exactly what you were wishing that "
extends" would do.Also, I should mention that you can have as many types as you want in the intersection type. So if you wanted, you could do:
[Note: this code sample should not be construed as an endorsement of the
Cloneableinterface; it was merely handy at the time.]JDK 7 的 JSR 203（新的新 IO）内容大量使用实现接口的枚举（例如：http://openjdk.java.net/projects/nio/javadoc/java/nio/file/FileVisitOption.html) 允许它们进行一些摆动将来有空间用于未来额外的枚举选项集。 因此，这是一种可行的方法，并且显然是在一个大型 Sun 项目中经过深思熟虑后选择的方法。
The JSR 203 (new new IO) stuff for JDK 7 is making a lot of use of enums that implement interfaces (for example: http://openjdk.java.net/projects/nio/javadoc/java/nio/file/FileVisitOption.html) to allow them some wiggle room in the future for future additional sets of enum options. So that is a feasible approach and obviously one that was chosen after a lot of thought in one large Sun project.