DefensiveName.java

/** Immutable name */
public class DefensiveName {
  private String first;
  private String last;

  public DefensiveName(String first, String last) {
    if (first == null) throw new IllegalArgumentException("first may not be null");
    if (last == null) throw new IllegalArgumentException("last may not be null");

    this.first = first;
    this.last = last;
  }
  public String getFirst() { return first; }
  public String getLast() { return last; }

  public String toString() { return first + " " + last; }
  public boolean equals(Object o) {
    if (o == null) return false;
    if (!o.getClass().equals(getClass()) return false;

    DefensiveName other = (DefensiveName)o;
    return getFirst().equals(other.getFirst()) && 
           getLast().equals(other.getLast());
  }
  public int hashCode() {
    return getFirst().hashCode() + getLast().hashCode();
  }
}

OffensiveName.java

/** Immutable name */
public class OffensiveName {
  private String first;
  private String last;

  public OffensiveName(String first, String last) {
    if (first == null) throw new IllegalArgumentException("first may not be null");
    if (last == null) throw new IllegalArgumentException("last may not be null");

    this.first = first;
    this.last = last;
  }
  public String getFirst() { return first; }
  public String getLast() { return last; }

  public String toString() { 
    return (getFirst() == null ? "" : getFirst()) + " " 
           + (getLast() == null ? "" : getLast()); 
  }

  public boolean equals(Object o) {
    if (o == null) return false;
    if (!o.getClass().equals(getClass()) return false;

    DefensiveName other = (DefensiveName)o;

    boolean firstEqual = getFirst() == null ? getFirst() == other.getFirst() : getFirst().equals(other.getFirst());
    boolean lastEqual = getLast() == null ? getLast() == other.getLast() : getLast().equals(other.getLast());
    return firstEqual && lastEqual
  }
  public int hashCode() {
    return (getFirst() == null ? 0 : getFirst().hashCode() )
        + getLast() == null ? 0 : getLast().hashCode());
  }
}