java - 抽象 compareTo 方法未被覆盖

Question

编译下面的代码时，出现以下错误:

PersonalInformation is not abstract and does not override abstract method compareTo(Object) in Comparable

我认为这意味着我的 compareTo 方法有问题。但一切似乎都还好。有人有什么建议吗？

import java.util.*;
public class PersonalInformation implements Comparable
{
private String givenName;
private String middleInitial;
private String surname;
private String gender;
private String emailAddress;
private String nationalId;
private String telephoneNum;
private String birthday;

public PersonalInformation(String gN, String mI, 
        String sur, String gen, String eMa, String natId,
        String teleNum, String birthd)

{
        givenName = gN;
        middleInitial = mI;
        surname = sur;
        gender = gen;
        emailAddress = eMa;
        nationalId = natId;
        telephoneNum = teleNum;
        birthday = birthd;


}


public int compareTo(PersonalInformation pi)
{
 return (this.gender).compareTo(pi.gender);
}

}

Answer 1

这样做:

public int compareTo(Object pi) {
    return ((PersonalInformation )(this.gender)).compareTo(((PersonalInformation ) pi).gender);
}

或更好

public class PersonalInformation implements Comparable<PersonalInformation>

如果您实现Comparable 接口(interface)，则必须使用第一种方法为所有对象实现它，或者以第二种方式键入您的类。