java - 联系人无法转换为 java.lang.Comparable

Question

我一直在努力发现我的错误，但无济于事。有人能帮我吗？ 我确信我正在比较正确的对象

    Contact[] sortedList = myContactList.sortContactsByName();
    for (Contact c : sortedList) {
        // TODO using this line means you need to implement what in Contact class?
        // Hint: You need to override a method inherited from Object.

        System.out.println(c);
    }
}



public Contact[] sortContactsByName() {
    Contact[] contactArray = contacts.toArray(new Contact[contacts.size()]);
    // TODO Contact class has to implement Comparable
    // interface for this to work!

    Arrays.sort(contactArray);
    // Don't bother how it works now, sorting in Java
    // will be covered later on.
    return contactArray;
}

}

public int compareTo(Contact o1){

    return this.name.compareTo( o1.name);

Answer 1

您必须声明类Contact 才能实现Comaprable。

class Contact implements Comparable<Contact> {

如果没有此声明，仅实现 compareTo 是不够的。另外，在 compareTo 上方放置 @Override 注释也是一种很好的做法。