Chapeter 4 Classes and Interfaces

Item 17: Design and document for inheritance or else prohibit it

• 1.the class must document its self-use of overridable methods.

• 2.a class may have to provide hooks into its internal workings in the form of judiciously chosen protected methods

• 3. The only way to test a class designed for inheritance is to write subclasses.

• 4. Constructors must not invoke overridable methods, directly or indirectly

• 5. It is generally not a good idea for a class designed for inheritance to implement either of these interfaces

  • The Cloneable and Serializable interfaces present special difficulties when designing for inheritance.
  • If you do decide to implement Cloneable or Serializable
    • neither clone nor readObject may invoke an overridable method, directly or indirectly

• 6.prohibit subclassing: all the constructors private or package-private and to add public static factories in place of the constructors

• 7. If you feel that you must allow inheritance from a concrete class does not implement a standard interface, ensure that the class never invokes any of its overridable methods and to document this fact.

  • eliminate the class’s self-use of overridable methods entirely