Java-polymorphic "excerpt"

means that objects of different classes are allowed to respond to the same message. That is, the same message can be used in a variety of different ways depending on the sending object. (Sending a message is a function call).

　　

1. the technique of implementing polymorphism is called dynamic binding, which refers to the actual type of the referenced object during execution, and calls its corresponding party according to its actual type.
2. the role of polymorphism: to eliminate the coupling relationship between types.

Three necessary conditions for polymorphic existence
First, to have inheritance;
Second, to have a rewrite;
The parent class reference points to the subclass object.

　　

Benefits of polymorphism:

1. Replaceable (substitutability). Polymorphism is replaceable for existing code. For example, polymorphism works on the Circle Circle class and works on any other circular geometry, such as a ring.
2. expandability (Extensibility). Polymorphism has extensibility for code. Adding new subclasses does not affect the polymorphism, inheritance, and the operation and manipulation of other attributes of existing classes. In fact, new subclasses are more likely to get polymorphic functions. For example, it is easy to add the polymorphism of sphere class on the basis of realizing the multi-state of cone, semi-cone and hemispherical body.
3. Interface (interface-ability). Polymorphism is a superclass that, by way of signature, provides a common interface to subclasses, which is implemented by subclasses to refine or overwrite the class. As shown in 8.3. The super-Class shape in the figure specifies two interface methods for implementing polymorphism, Computearea () and Computevolume (). Subclasses, such as circle and sphere, refine or overwrite both interface methods in order to achieve polymorphism.
4. Flexibility (flexibility). It embodies the flexible operation in the application, and improves the use efficiency.
5. Simplification (simplicity). Polymorphism simplifies the process of coding and modifying the application software, especially when dealing with the operation and operation of a large number of objects.

From Jack204

Java-polymorphic "excerpt"