Use of comparable (for arrays.sort)

package snippet;
import java.util.Arrays;
/**
 *  Use Comparable Interface ： Let the class of the object to be sorted implement Comparable Interface , And rewrite Comparable Interface compareTo() Method 
 *  The disadvantage is that you can only sort by one rule 
 * @author tong
 *
 */
public class Compara {

    public static void main(String[] args) {
        Person[] persons = new Person[5];
        persons[0] =new Person("tom",45);
        persons[1] =new Person("jack",12);
        persons[2] =new Person("bill",21);
        persons[3] =new Person("kandy",34);
        persons[4] =new Person();
        // The key 
        Arrays.sort(persons);
        for (Person person:persons) {
            System.out.println(person);
        }
    }
}

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Here is inheritance Comparable Of Person class ：

package snippet;

class Person implements Comparable<Person>{
    private String name;
    private int age;

    public Person(String name,int age){
        this.name = name;
        this.age = age;
    }
    public Person(){
        this("unknown", 0);
    }

    // rewrite Student Class toString() Method , When you import an object, output it as follows 
    @Override
    public String toString() {      
        return "Person[name:"+name+",age:"+age+"]";
    }

    // Override the compareTo() Method , Sort them in descending order 
    @Override
    public int compareTo(Person o) {
         return age-o.age;
    }
}

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Output results ：

Person[name:unknown,age:0]
Person[name:jack,age:12]
Person[name:bill,age:21]
Person[name:kandy,age:34]
Person[name:tom,age:45]

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