Java 泛型问题:类“不在类型变量的范围内"错误. [英] Java generics issue: Class "not within bounds of type-variable" error.

问题描述

我正在做一个涉及泛型的类项目.

I'm working on a project for class that involves generics.

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;
        ...
    }
}

在 MySearchTree 的声明中尝试使用 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.

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.

有什么想法吗?

推荐答案

在MySearchTree中，基本类型的K是Course.所以K必须扩展"Comparable>&Keyable<课程>.但它没有，它扩展了 Comparable>&Keyable.

In MySearchTree the K of the base type is Course. So K must "extend" Comparable<Keyable<Course>> & Keyable<Course>. But it doesn't, it extends Comparable<Keyable<DataElement>> & Keyable<DataElement>.

我想 DataElement 应该以类似于 Comparable 或 的方式进行泛化枚举.

I guess DataElement should be generified in a similar manner to Comparable or 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> {

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