gistfile1.java

import java.util.*;

class Person {
  private String firstname;
  private String secondname;
  
  Person() {
    //default constructor
  }
  
  Person(String firstname, String secondname) {
    this.firstname = firstname;
    this.secondname = secondname;
  }
  
  void getPerson() {
    this.firstname = Console.readToken();
    this.secondname = Console.readToken();
  }
  
  String putName() {
    return secondname + ", " + firstname;
  }
}

class PersonComparable implements Comparator<Person> {
  @Override
    public int compare(Person p1, Person p2) {
      return p1.putName().compareTo(p2.putName());
    }
}

class Ex1 {
  public static void main(String[] args) {
    ArrayList<Person> people = new ArrayList<Person>();
    while(!Console.endOfFile()) {
      Person tmp = new Person();
      tmp.getPerson();
      people.add(tmp);
    }
    Collections.sort(people, new PersonComparable());
    for(Person p : people) {
      System.out.println(p.putName());
    }
  }
}