抽象compareTo方法没有被覆盖

Question

编译下面的代码时,我收到以下错误:

PersonalInformation不是抽象的,并且不会覆盖Comparable中的抽象方法compareTo(Object)

我认为这意味着我的方法有问题compareTo.但一切似乎都没事.有人有建议吗？

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

做这个:

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

或更好

public class PersonalInformation implements Comparable<PersonalInformation>

如果实现了Comparable接口,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类.

Answer 2

再看看juergen的回答,好多了.

你正在重载方法:

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

而不是覆盖它:

public int compareTo(Object pi)

它可能是这样的:

public int compareTo(Object pi)
{
    if ( ! pi instanceof PersonalInformation )
        return false;
    return (this.gender).compareTo( (PersonalInformation)pi.gender );
}

Answer 3

您需要实现Comparable<PersonalInformation>而不是Comparable为您的类编译和工作.

如果您正在实现Comparable,那么compareTo(Object o)您的类中缺少预期的方法签名,从而导致错误.