14. Interface

 

1. abstract classes and interfaces

No.	Point of comparison	Abstract class	interface	Remark
1	Keyword	class	interface
2	concept	Can not be instantiated class may contain abstract methods.	The definition of standards, rules, agreements
3	Structure	Construction methods, common methods, static methods, abstract methods, member variables, static properties, constants	Static constants, abstract methods
4	And subclass relationships	Subclass inherits	The rules for implementing the interface implementation class
5	relationship	extends	implement
6	usage	Abstract class as a parent class, an abstract method,	Required to achieve the agreed class implements
7	Feature	Subclasses inherit only a single parent	Implementation class can implement multiple interfaces

Method two special interface

1. static method;

2. The default method: jdk1.8 version of the new features appear. Objective: To not mandatory to achieve a certain function.

2. The relationship between class and class

1, inheritance

Inheritance refers to a class inherits from another class. As a subclass, the other is the parent class. Subclass can use the content of the parent class, they can also expand their content. (Classes, interfaces)

 public class Animal{}
 public class Cat extends Animal{}

 

2, to achieve relations

It refers to a class implement all abstract methods implemented interface. A class can implement multiple interfaces simultaneously.

 public interface A{}
 public class AImple implements A{}

 

3, dependencies

A class dependent on another class. The degree of coupling between the two classes is not. Code levels reflect: a class as an argument of a method in another class.

 public class Pet{}
 public class Girl{
     public void play(Pet pet){
         
    }
 }

 

4, relationship

Dependencies between two classes relatively strong. Code levels reflect: a class as a property of another class.

 public class Book{}
 public class Person{
  Book book;
 }

 

Special relationship: polymerized composition. . .