Joshua Bloch

In cases where a class seems to require multiple constructors with the same signature, replace the constructors with static factory methods and carefully chosen names to highlight their differences.

equal objects must have equal hash codes.

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