Day_ thirteen

1. The relationship between classes

Inherit ：

key word ： extends

Class and class are single inheritance , Interface and interface are multi inheritance ,

 

 

Realization ：

key word ： implement

There are multiple implementations between classes and interfaces , Multiple are separated by commas Class Class name implements Interface , Interface ....{}

Class implements the interface , All abstract methods must be implemented , Otherwise, it is necessary to add abstract modification

 

rely on ：

relation ：

polymerization ：

Both the whole and the part have independent life cycles

Combine ：

Part and whole are inseparable , For example, the human body is a combination

2. Inner class

Definition ：

When the inside of a thing , There is another part that needs a complete structure to describe , And this inside The complete structure of the ministry only provides services for external things , Then the whole internal structure is better to make Use inner classes

stay Java in , Allow the definition of one class to be inside another class , The former is called the inner class , The latter is called the outer class .

Inner class It is generally used within the class or statement block that defines it , It must be given the full name when it is externally referenced .

Member inner class ：

Static inner class ：

 

Local inner classes ：

 

  Anonymous inner class ：

 
 3. Design patterns  

Starving model ：

The load phase creates objects

 

The sluggard model ：

        Create objects when you use them