Eq4.java

  public class Person {
    String firstName;
    String lastName;
    
    public final boolean equals(Object other) {
      if (this == other) {
        return true;
      }
      if (other == null) {
        return false;
      }
      if (!(other instanceof Person)) {
        return false;
      }
      Person person = (Person) other;
      return Objects.equals(firstName, person.firstName)
          && Objects.equals(lastName, person.lastName);
    }
  }