Java 泛型问题：类“不在类型变量范围内”错误。
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Java generics issue: Class "not within bounds of type-variable" error.
提问by SamWN
I'm working on a project for class that involves generics.
我正在研究一个涉及泛型的类项目。
public interface Keyable <T> {public String getKey();}
public interface DataElement extends Comparable<Keyable<DataElement>>, Keyable<DataElement>, Serializable {...}
public class Course implements DataElement {...}
public interface SearchTree<K extends Comparable<Keyable<K>> & Keyable<K>> extends Serializable {...}
public class MySearchTree implements SearchTree<Course> {
...
private class Node {
public Course data;
public Node left;
public Node right;
...
}
}
When trying to use the Course class within the declaration of MySearchTree, I receive a type argument error stating that "Course is not within the bounds of type-variable K". I spent a good amount of time trying to figure out what attributes Course might be lacking to make it not fit the bill, but came up empty.
当尝试在 MySearchTree 的声明中使用 Course 类时，我收到一个类型参数错误，指出“Course 不在类型变量 K 的范围内”。我花了很多时间试图弄清楚 Course 可能缺乏哪些属性使其不符合要求，但结果却是空洞的。
Any ideas?
有任何想法吗？
回答by Tom Hawtin - tackline
In MySearchTreethe Kof the base type is Course. So Kmust "extend" Comparable<Keyable<Course>> & Keyable<Course>. But it doesn't, it extends Comparable<Keyable<DataElement>> & Keyable<DataElement>.
在MySearchTree该K基本类型的是Course。所以K必须“扩展” Comparable<Keyable<Course>> & Keyable<Course>。但它没有，它扩展了Comparable<Keyable<DataElement>> & Keyable<DataElement>。
I guess DataElementshould be generified in a similar manner to Comparableor Enum.
我想DataElement应该以类似于Comparableor 的方式进行泛化Enum。
public interface Keyable <T> {public String getKey();}
public interface DataElement<THIS extends DataElement<THIS>> extends Comparable<Keyable<THIS>>, Keyable<THIS>, Serializable {...}
public class Course implements DataElement<Course> {...}
public interface SearchTree<K extends Comparable<Keyable<K>> & Keyable<K>> extends Serializable {...}
public class MySearchTree implements SearchTree<Course> {
