// source: http://onjava.com/pub/a/onjava/2003/03/12/java_comp.html?page=1

// This application demonstrates how to implement the compareTo( ) method to compare

// objects in an array.

//---------------------- class: person

class Person implements Comparable {

  private String firstName;

  private String lastName;

  private int age;

  public String getFirstName() {

    return firstName;

  }

  public void setFirstName(String firstName) {

    this.firstName = firstName;

  }

  public String getLastName() {

    return lastName;

  }

  public void setLastName(String lastName) {

    this.lastName = lastName;

  }

  public int getAge() {

    return age;

  }

  public void setAge(int age) {

    this.age = age;

  }

  public int compareTo(Object anotherPerson) throws ClassCastException {

    if (!(anotherPerson instanceof Person))

      throw new ClassCastException("A Person object expected.");

    int anotherPersonAge = ((Person) anotherPerson).getAge(); 

    return this.age - anotherPersonAge;   

  }

}

//---------------------- class: ComparableTesting (with the main( ) method)

import java.util.Arrays;

import java.util.ArrayList;

public class ComparableTesting {

  public static void main(String[] args) {

    Person[] persons = new Person[4];

    persons[0] = new Person();

    persons[0].setFirstName("Elvis");

    persons[0].setLastName("Goodyear");

    persons[0].setAge(56);

    persons[1] = new Person();

    persons[1].setFirstName("Stanley");

    persons[1].setLastName("Clark");

    persons[1].setAge(8);

    persons[2] = new Person();

    persons[2].setFirstName("Jane");

    persons[2].setLastName("Graff");

    persons[2].setAge(16);

    persons[3] = new Person();

    persons[3].setFirstName("Nancy");

    persons[3].setLastName("Goodyear");

    persons[3].setAge(69);

    System.out.println("Natural Order");

    for (int i=0; i<4; i++) {

      Person person = persons[i];

      String lastName = person.getLastName();

      String firstName = person.getFirstName();

      int age = person.getAge();

      System.out.println(lastName + ", " + firstName + ". Age:" + age);

    }

    Arrays.sort(persons); // sort the array of Person

    System.out.println();

    System.out.println("Sorted by age");

    //for (int i=0; i<4; i++) {

    //  Person person = persons[i];

    for (Person person : persons) {

      String lastName = person.getLastName();

      String firstName = person.getFirstName();

      int age = person.getAge();

      System.out.println(lastName + ", " + firstName + ". Age:" + age);

    }

  }

}