Joshua Bloch

well-designed component hides all its implementation details, cleanly separating its API from its implementation. Components then communicate only through their APIs and are oblivious to each others’ inner workings. This concept, known as information hiding or encapsulation

the equality test imposed by the compareTo method should generally return the same results as the equals method

Use of the relational operators < and > in compareTo methods is verbose and error-prone and no longer recommended.