Not all equals Methods are Simple

• Two sets are equal if they have the same elements in some order
  

  public boolean equals(Object o) 
  { 
     if (o == this) return true; 
     if (!(o instanceof Set)) return false; 
     Collection c = (Collection) o; 
     if (c.size() != size()) return false; 
     return containsAll(c); 
  }