/** Person is a class that represents a human being. */
public class Person {
  // Data Fields
  /** The given name */
  private String givenName;
  
  /** The family name */
  private String familyName;
  
  /** The ID number */
  private String IDNumber;
  
  /** The birth year */
  private int birthYear = 1900;
  
  // Constants
  /** The age at which a person can vote */
  private static final int VOTE_AGE = 18;
  
  /** The age at which a person is considered a senior citizen */ 
  private static final int SENIOR_AGE = 65;
  
  // Constructors
  /** Construct a person with given values
   @param first The given name
   @param family The family name
   @param ID The ID number
   @param birth The birth year
   */
  public Person(String first, String family, String ID, int birth) {
    givenName = first;
    familyName = family;
    IDNumber = ID;
    birthYear = birth;
  }
  
  /** Construct a default person. */
  public Person() { }
  
  // Modifier Methods
  /** Sets the givenName field.
   @param given The given name
   */
  public void setGivenName(String given) {
    givenName = given;
  }
  
  /** Sets the familyName field.
   @param family The family name
   */
  public void setFamilyName(String family) {
    familyName = family;
  }
  
  /** Sets the IDNumber field.
   @param ID The ID number
   */
  public void setIDNumber(String ID) {
    IDNumber = ID;
  }
  
  /** Sets the birthYear field.
   @param birthYear The year of birth
   */
  public void setBirthYear(int birthYear) {
    this.birthYear = birthYear;
  }
  
  // Accessor Methods 
  /** Gets the person's given name.
   @return the given name as a String 
   */
  public String getGivenName() { return givenName; }
  
  /** Gets the person's family name.
   @return the family name as a String
   */
  public String getFamilyName() { return familyName; }
  
  /** Gets the person's ID number.
   @return the ID number as a String
   */
  public String getIDNumber() { return IDNumber; }
  
  /** Gets the person's year of birth.
   @return the year of birth as an int value
   */
  public int getBirthYear() { return birthYear; }
  
  // Other Methods
  /** Calculates a person's age at this year's birthday.
   @param year The current year
   @return the year minus the birth year
   */
  public int age(int year) {
    return year - birthYear;
  }
  
  /** Determines whether a person can vote.
   @param year The current year
   @return true if the person's age is greater than or
   equal to the voting age
   */
  public boolean canVote(int year) {
    int theAge = age (year);
    return theAge >= VOTE_AGE;
  }
  
  /** Determines whether a person is a senior citizen.
   @param year the current year
   @return true if person's age is greater than or
   equal to the age at which a person is considered to be a senior citizen
   */
  public boolean isSenior(int year) {
    return age (year) >= SENIOR_AGE; }
  
  /** Retrieves the information in a Person object.
   @return the object state as a string
   */
  public String toString() {
    return "Given name: " + givenName + "\n"
      + "Family name: " + familyName + "\n" + "ID number: " + IDNumber + "\n"
      + "Year of birth: " + birthYear + "\n";
  }
  
  /** Compares two Person objects for equality. 
   @param per The second Person object
   @return true if the Person objects have same
   ID number; false if they don't
   */
  public boolean equals(Person per) {
    if (per == null)
      return false;
    else
      return IDNumber.equals(per.IDNumber);
  }
}