1.定義：高層模塊不應該依賴低層模塊，二者都應該依賴其抽象

2.抽象不應該依賴細節，細節應該依賴抽象

3.針對接口編程，不要針對實現編程

4.優點：可以減少類間的耦合性、提高系統穩定性，提高代碼可讀性和可維護性，可降低修改程序所造成的風險

5.實例目錄package

6.UML類圖

7.代碼

1 package com.geely.design.principle.dependenceinversion;
2 
3 public interface ICourse {
4     void studyCourse();
5 }

1 package com.geely.design.principle.dependenceinversion;
 
2 
3 public class JavaCourse implements ICourse{
4     public void studyCourse() {
5         System.out.println("Geely在學習Java課程");
6     }
7 }

1 package com.geely.design.principle.dependenceinversion;
2 
3 public class PythonCourse implements ICourse {
4     public void studyCourse() {
5         System.out.println("Geely在學習Python課程");
 
6     }
7 }

1 package com.geely.design.principle.dependenceinversion;
2 
3 public class FECourse implements ICourse {
4     public void studyCourse() {
5         System.out.println("Geely在學習FE課程");
6     }
7 }

 1 package com.geely.design.principle.dependenceinversion;
 2 
 3 public class Geely {
 
 4     private ICourse iCourse;
 5 
 6     public Geely(){
 7 
 8     }
 9     public Geely(ICourse iCourse){
10         this.iCourse = iCourse;
11     }
12     public void studyImoocCourse(){//ICourse iCourse
13         iCourse.studyCourse();
14     }
15 
16     public void setiCourse(ICourse iCourse){
17         this.iCourse = iCourse;
18     }
19     /*public void studyJavaCourse(){
20         System.out.println("Geely在學習Java課程");
21     }
22     public void studyFECourse(){
23         System.out.println("Geely在學習FE課程");
24     }
25     public void studyPythonCourse(){
26         System.out.println("Geely在學習Python課程");
27     }*/
28 }

 1 package com.geely.design.principle.dependenceinversion;
 2 
 3 public class Test {
 4     public static void main(String[] args){
 5         /*Geely geely = new Geely();
 6         geely.studyJavaCourse();
 7         geely.studyFECourse();
 8         geely.studyPythonCourse();*/
 9 
10         /*Geely geely = new Geely();
11         geely.studyImoocCourse(new JavaCourse());
12         geely.studyImoocCourse(new FECourse());
13         geely.studyImoocCourse(new PythonCourse());*/
14 
15         /*Geely geely = new Geely(new JavaCourse());
16         geely.studyImoocCourse();
17         Geely geely2 = new Geely(new FECourse());
18         geely2.studyImoocCourse();*/
19 
20         Geely geely = new Geely();
21         geely.setiCourse(new JavaCourse());
22         geely.studyImoocCourse();
23         geely.setiCourse(new FECourse());
24         geely.studyImoocCourse();
25     }
26 }

依賴倒置原則