/** Class for a directory storing pairs pf Person objects. */
public class PersonPairDirectory {

  // instance variables...

  public PersonPairDirectory() {
    // constructor code body...
  }

  public void insert (Person person, Person other) {
    // insertion code for a person pair...
  }

  public Person findOther (Person person) {
    // code for finding a pair containing person... (uses equalTo)
    return null; // stub to make this class compile successfully
  }

  public void remove (Person person, Person other) {
    // code for removing a specified person pair...
  }
}