Реализация интерфейса Comparable

Помогите реализовать интерфейс для класса Per интерфейс Comparable.

import java.util.Arrays; 
import java.util.Collections; 
import java.util.Comparator; 
import java.util.List;
public class ComparatorDemo {    
    public static void main(String[] args) {        
        List<Person> people = Arrays.asList(                
            new Person("Joe", 24),                
            new Person("Pete", 18),                
            new Person("Chris", 21)        
            );        
        Collections.sort(people, new LexicographicComparator());        
        System.out.println(people);        
        Collections.sort(people, new AgeComparator());        
        System.out.println(people);    
    } 
}
class LexicographicComparator implements Comparator<Person> {    
    @Override    
    public int compare(Person a, Person b) {        
        return a.name.compareToIgnoreCase(b.name);    
    } 
}
class AgeComparator implements Comparator<Person> {    
    @Override    
    public int compare(Person a, Person b) {        
        return a.age < b.age ? -1 : a.age == b.age ? 0 : 1;    
    } 
}
class Per {
    String name;    
    int age;
    Person(String n, int a) {        
        name = n;        
        age = a;    
    }
    @Override    
    public String toString() {        
        return String.format("\nname=%s, age=%d", name, age);    
    } 
}