Person.java

import java.util.Comparator;
import java.util.List;
import java.util.Arrays;
import java.util.Collections;

public class Person implements Comparable<Person> {

    private String name;
    private int age;

    Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    String getName() {
        return this.name;
    }

    int getAge() {
        return this.age;
    }

    public int compareTo(Person o) {
        return new Integer(this.age).compareTo(o.getAge());
    }

    @Override
    public String toString() {
        return this.name + ":" + this.age;
    }

    public static void main(String[] args) {
        System.out.println(new Person("Tarou", 10).compareTo(new Person("Saburou", 30)));

        List<Person> persons = Arrays.asList(
                new Person("Saburou", 30),
                new Person("Jiro", 20),
                new Person("Tarou", 10),
                new Person("Hanako", 30));

        Collections.sort(persons);
        System.out.println(persons);

        Collections.sort(persons, new Comparator<Person>() {
            public int compare(Person o1, Person o2) {
                int c = new Integer(o1.getAge()).compareTo(o2.getAge());
                if (c != 0) {
                    return c;
                } else {
                    return o1.getName().compareTo(o2.getName());
                }
            }
        });
        System.out.println(persons);
    }
}