/**
* The combination of the dimit rule (high cohesion principle) and the dependency inversion principle (image extraction layer application)
* (This idea runs through the entire design model)
* From <Java and mode>.
*CodeAnd Annotations: if it is not cold
* Note: Zhang sanli 4 is a friend relationship, while Li siwang 5 is a friend relationship. Zhang Sanhe and Wang 5 are strangers.
* To ensure that Zhang Sanhe and Wang wuzhong do not know each other, Zhang Sanhe can call the methods in Wang wuzhong.
* Use Li Si as a relay to isolate Zhang San and Wang Wu
First look at his UML diagram */
Public interface abstractstranger // specifies the target image, a stranger;
{
Abstract void operation3 ();
}
//---------------------------------
Public class someone // someone; (James)
{
Public void operation1 (friend)
{
Abstractstranger stranger = friend. Provide (); // Rishi replacement;
Stranger. operation3 ();
}
}
//---------------------------------
Public class friend // friend; (Li Si)
{
Private abstractstranger stranger = new stranger ();
Public void operation2 ()
{
System. Out. println ("operation2 ");
}
Public abstractstranger provide ()
{
Return stranger;
}
}
//---------------------------------
Public class stranger implements abstractstranger
{// Stranger (Wang Wu );
Public void operation3 ()
{
System. Out. println ("operation3 ");
}
} Dependency inversion principle: It depends on abstraction and not on specifics. 8.3 dependency reversal Principle
Three Coupling Relationships:
1) Zero Coupling
2) specific coupling: occurs between two (instantiated) classes.
3) Abstract coupling: occurs between a specific class and an abstract class (or Java interface. What?
Abstraction should not depend on details; details should depend on abstraction. Another statement:
Do not implement programming for the interface.
A specific Java class should only implement Java interfaces and Abstract METHODS declared in the Java class, and should not provide redundant methods. Static type of a variable: the type of the variable when it is declared.
True Type of a variable: The True Type of the object referenced by the variable. The abstract type of the referenced object.
In many cases, a JavaProgramYou need to reference an object. At this time, if this object has an abstract type, you should use this abstract typeStatic variable type. This isInterface Programming.
Example: Egg x = new chicken ();
Instead of: Chicken x = new chicken (); List employees = new vector ();
Instead of: vector employees = new vector (); |
