java - 当我已经有时，编译器告诉我实现compareTo()方法

Question

我有以下类，它实现了Comparable接口(interface)。我已经在其中定义了 compareTo() 方法，但编译器仍然告诉我必须实现它。

public class Person implements Comparable { 
    private String fName;
    private String lName;
    private Integer age;
    public Person (String fName, String lName, int age)
    {
        this.fName = fName;
        this.lName = lName;
        this.age = age;
    }

    // Compare ages, if ages match then compare last names
    public int compareTo(Person o) {
        int thisCmp = age.compareTo(o.age);        
        return (thisCmp != 0 ? thisCmp : lName.compareTo(o.Name));
    }
}

错误信息:

The type Person must implement the inherited abstract method Comparable.compareTo(Object)
Syntax error on token "=", delete this token
    at me.myname.mypkg.Person.<init>(Person.java:6)

我非常肯定我不必在 compareTo() 方法中转换为根类 Object。那么我可能做错了什么？

Answer 1

如果你要使用 Generic 那么你的类看起来像这样

class Person implements Comparable<Person> {

    private String fName;
    private String lName;
    private Integer age;

    public int compareTo(Person o) {
        int thisCmp = age.compareTo(o.age);        
        return (thisCmp != 0 ? thisCmp : lName.compareTo(o.fName));
     }      
}

如果你不使用 Generic 那么你的类看起来像

class Person implements Comparable {

    private String fName;
    private String lName;
    private Integer age;    
    public int compareTo(Object  obj) {
        Person o= (Person) obj;
        int thisCmp = age.compareTo(o.age);        
        return (thisCmp != 0 ? thisCmp : lName.compareTo(o.fName));
     }  
}