Thinking in Java note three

The eighth chapter Polymorphic

Polymorphism is the third basic feature following data abstraction and inheritance

8.1 Further discussion upward transformation

8.2 Connections

Method call binding, except that Java and final (private method belongs to the final method) all other methods are late-bound

Polymorphism is an important technique for separating changed things from unchanging things.

Do not attempt to overwrite the base class private method, but only in such a way as to produce a completely new method

The access operation of a domain is not polymorphic by the compiler, nor is the static method polymorphic

8.3 Constructors and Polymorphic

Constructor Call Order P159

If cleanup is required, the base class cleanup method is called when the subclass overrides the base-class cleanup method, after it has cleaned itself out

Try to avoid calling other methods inside the constructor (if generating polymorphism can cause positional errors)

8.4 Covariant return type

Overridden methods in an exported class can return some type of export of a base class method return type

8.5 Design with inheritance

Prioritize use of combinations rather than inheritance

Use inheritance to represent differences between behaviors, and to express changes in state with fields

Pure Inheritance (is-a) and extension (is-like-a), down transformation with runtime type recognition

Nineth Chapter Interface

Interfaces and internal classes provide us with a more structured approach to separating interfaces from implementations

9.1 Abstract classes and abstract methods

A basic form is established through an interface, which represents the common part of all exported classes

Abstract classes and abstract methods can clarify the abstraction of a class and tell the user and the compiler how to use them

9.2 interface

Interfaces are used to establish the protocol between classes

The interface domain is implicitly static and final.

Policy mode, different implementations of the delivery interface show different behavior

Adapter mode, adapting an existing implementation to a new interface

9.3 Complete Decoupling

9.4 Multiple inheritance in Java

Implementing multiple interfaces

9.5 Extending the interface through inheritance

Inheriting multiple interfaces allows the same method to be included, but only a different method of return type is indistinguishable

9.6 Adapter Interface

Getting a method to accept an interface type is a way for any class to adapt the method, which is the power of using the interface

Domains in the 9.7 interface

cannot be null, can be initialized by a very expressive expression

is not part of the interface and the value is stored in the static storage domain of the interface

9.8 Nested interfaces

9.9 Interfaces and factories

Factory Method Design Pattern

Any abstraction should be the result of real demand, and it is necessary to consider refactoring interfaces rather than adding extra levels of indirection

The appropriate principle is to prioritize the class rather than the interface, and if the requirements of the interface become very clear, then refactor

Tenth chapter Inner class

Place the definition of a class inside another class. Organize some logically related classes together and control the visibility of classes that are in-house

10.1 Creating an inner class

10.2 Connecting to an external class

The inner class automatically has access to all members of its perimeter class, and the inner class object has this reference to the Outer class object

10.3 using the. This and. New

Creating an inner class object using an external class object

10.4 Internal classes and upward transformation

10.5 Inner classes within methods and scopes

10.6 Anonymous Inner class

10.7 Nested Classes

Inner class declared as static

10.8 Why internal classes are required

The inner class provides some kind of window into the perimeter class.

Closures and callbacks, control framework

10.9 Inheritance of inner classes

10.10 Overriding of inner classes

Covering the inner class as if it were a method of the perimeter class, and it doesn't work.

10.11 local Inner class

10.12 Internal class identifier

External class plus $

Thinking in Java note three