为什么Java类应实现可比性？

这是一个真实的例子。请注意，它

String

Comparable

class Author implements Comparable<Author>{    String firstName;    String lastName;    @Override    public int compareTo(Author other){        // compareTo should return < 0 if this is supposed to be        // less than other, > 0 if this is supposed to be greater than         // other and 0 if they are supposed to be equal        int last = this.lastName.compareTo(other.lastName);        return last == 0 ? this.firstName.compareTo(other.firstName) : last;    }}

后来..

public List<Author> listAuthors(){    List<Author> authors = readAuthorsFromFileOrSomething();    Collections.sort(authors);    return authors;}public SortedSet<Author> listUniqueAuthors(){    List<Author> authors = readAuthorsFromFileOrSomething();    return new TreeSet<Author>(authors);}