本文探讨了Java中Comparable接口的使用，通过示例展示了如何创建一个可比较的SortableStack接口。作者指出，当实现Comparable时，类型E必须能够与自身比较，这可能导致递归类型定义的问题。同时，文章提到了一个不合规的实现，即UncomparableUser类，它实现了Comparable但比较的对象类型不正确，导致无法在Collections.sort()中使用。博客强调了正确实现Comparable的重要性及其在排序中的作用。
I tried to create an interface ISortableStack using > but I can't move forward. What does the following do?
>
I've tried this, but it doesn't help.
解决方案
> means that E must be a type that knows how to compare to itself, hence, the recursive type definition.
public class Comparables {
static class User implements Comparable {
@Override
public int compareTo(User user) {
return 0;
}
}
/**
* This class cannot be used with Collections.sort because an
* UncomparableUser is not comparable with itself. However, notice
* that you get no compiler error just for implementing
* Comparable.
*/
static class UncomparableUser implements Comparable {
@Override
public int compareTo(String user) {
return 0;
}
}
public static void main(String[] args) {
List users = Arrays.asList(new User());
// Using this would cause a compiler error
// List users = Arrays.asList(new UncomparableUser());
Collections.sort(users);
}
}
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