基本介绍

  1. 客户端不应该不依赖它不需要的接口，即一个类对另一个类的依赖（使用调用）应该建立在最小的接口上
  2. 先看一张图：image.png
  3. 类A通过接口Interface1依赖B，类C通过接口Interface1依赖D，如果Interface1对于类A和类C来说不是最小接口，那么类B和类D必须去实现他们不需要的方法

  4. 按接口隔离原则应该这样处理：

    将接口Interface1拆分成独立的几个接口（这里我们拆分成3个接口），类A和类C分别于他们需要的接口建立依赖关系。也就是接口隔离原则。

应用实例

方案一：

类A通过接口Interface1依赖B，类C通过Interface1依赖D

  1. public class Application {
  3.     这种方式违背了接口隔离原则
  4.         一个类对另一个类的依赖（使用调用）应该建立在最小的接口上
  5.      类A通过接口Interface1依赖B，那么对于A来说类B就不用实现A不需要的方法同理C也是一样
  6.     public static void main(String[] args)  {
  8.         A a = new A();
  9.         a.depend1(new B());
  10.         a.depend2(new B());
  11.         a.depend3(new B());
  13.         C c = new C();
  14.         c.depend1(new D());
  15.         c.depend4(new D());
  16.         c.depend5(new D());
  17.     }
  18. }
  19. interface Interface1 {
  20.     void operation1();
  21.     void operation2();
  22.     void operation3();
  23.     void operation4();
  24.     void operation5();
  25. }
  27. class B implements Interface1 {
  29.     @Override
  30.     public void operation1() {
  31.         System.out.println("类B 实现接口operation1 方法");
  32.     }
  34.     @Override
  35.     public void operation2() {
  36.         System.out.println("类B 实现接口operation2方法");
  38.     }
  40.     @Override
  41.     public void operation3() {
  42.         System.out.println("类B 实现接口operation3方法");
  44.     }
  46.     @Override
  47.     public void operation4() {
  48.         System.out.println("类B 实现接口operation4方法");
  49.     }
  51.     @Override
  52.     public void operation5() {
  53.         System.out.println("类B 实现接口operation5方法");
  54.     }
  55. }
  57. class D implements Interface1 {
  59.     @Override
  60.     public void operation1() {
  61.         System.out.println("类D 实现接口operation1 方法");
  62.     }
  64.     @Override
  65.     public void operation2() {
  66.         System.out.println("类D 实现接口operation2方法");
  68.     }
  70.     @Override
  71.     public void operation3() {
  72.         System.out.println("类D 实现接口operation3方法");
  74.     }
  76.     @Override
  77.     public void operation4() {
  78.         System.out.println("类D 实现接口operation4方法");
  79.     }
  81.     @Override
  82.     public void operation5() {
  83.         System.out.println("类D 实现接口operation5方法");
  84.     }
  85. }
  86. class A {
  87.     public void depend1(Interface1 interface1){
  88.         interface1.operation1();
  89.     }
  90.     public void depend2(Interface1 interface1){
  91.         interface1.operation2();
  92.     }
  93.     public void depend3(Interface1 interface1){
  94.         interface1.operation3();
  95.     }
  97. }
  98. class C {
  99.     public void depend1(Interface1 interface1){
  100.         interface1.operation1();
  101.     }
  102.     public void depend4(Interface1 interface1){
  103.         interface1.operation4();
  104.     }
  105.     public void depend5(Interface1 interface1){
  106.         interface1.operation5();
  107.     }
  109. }

运行结果：

  1. "F:\Program Files\Java\jdk1.8.0_201\bin\java.exe" "-javaagent:F:\Program Files\JetBrains\IntelliJ IDEA 2018.3\lib\idea_rt.jar=50801:F:\Program Files\JetBrains\IntelliJ IDEA 2018.3\bin" -Dfile.encoding=UTF-8 -classpath "F:\Program Files\Java\jdk1.8.0_201\jre\lib\charsets.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\deploy.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\access-bridge-64.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\cldrdata.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\dnsns.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\jaccess.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\jfxrt.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\localedata.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\nashorn.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunec.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunjce_provider.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunmscapi.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunpkcs11.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\zipfs.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\javaws.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\jce.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\jfr.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\jfxswt.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\jsse.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\management-agent.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\plugin.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\resources.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\rt.jar;E:\study\study_jvm\target\classes;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot-starter-web\2.4.1\spring-boot-starter-web-2.4.1.jar;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot-starter\2.4.1\spring-boot-starter-2.4.1.jar;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot\2.4.1\spring-boot-2.4.1.jar;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot-autoconfigure\2.4.1\spring-boot-autoconfigure-2.4.1.jar;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot-starter-logging\2.4.1\spring-boot-starter-logging-2.4.1.jar;F:\JAVA\Maven\Repository\ch\qos\logback\logback-classic\1.2.3\logback-classic-1.2.3.jar;F:\JAVA\Maven\Repository\ch\qos\logback\logback-core\1.2.3\logback-core-1.2.3.jar;F:\JAVA\Maven\Repository\org\apache\logging\log4j\log4j-to-slf4j\2.13.3\log4j-to-slf4j-2.13.3.jar;F:\JAVA\Maven\Repository\org\apache\logging\log4j\log4j-api\2.13.3\log4j-api-2.13.3.jar;F:\JAVA\Maven\Repository\org\slf4j\jul-to-slf4j\1.7.30\jul-to-slf4j-1.7.30.jar;F:\JAVA\Maven\Repository\jakarta\annotation\jakarta.annotation-api\1.3.5\jakarta.annotation-api-1.3.5.jar;F:\JAVA\Maven\Repository\org\yaml\snakeyaml\1.27\snakeyaml-1.27.jar;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot-starter-json\2.4.1\spring-boot-starter-json-2.4.1.jar;F:\JAVA\Maven\Repository\com\fasterxml\jackson\core\jackson-databind\2.11.3\jackson-databind-2.11.3.jar;F:\JAVA\Maven\Repository\com\fasterxml\jackson\core\jackson-annotations\2.11.3\jackson-annotations-2.11.3.jar;F:\JAVA\Maven\Repository\com\fasterxml\jackson\core\jackson-core\2.11.3\jackson-core-2.11.3.jar;F:\JAVA\Maven\Repository\com\fasterxml\jackson\datatype\jackson-datatype-jdk8\2.11.3\jackson-datatype-jdk8-2.11.3.jar;F:\JAVA\Maven\Repository\com\fasterxml\jackson\datatype\jackson-datatype-jsr310\2.11.3\jackson-datatype-jsr310-2.11.3.jar;F:\JAVA\Maven\Repository\com\fasterxml\jackson\module\jackson-module-parameter-names\2.11.3\jackson-module-parameter-names-2.11.3.jar;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot-starter-tomcat\2.4.1\spring-boot-starter-tomcat-2.4.1.jar;F:\JAVA\Maven\Repository\org\apache\tomcat\embed\tomcat-embed-core\9.0.41\tomcat-embed-core-9.0.41.jar;F:\JAVA\Maven\Repository\org\glassfish\jakarta.el\3.0.3\jakarta.el-3.0.3.jar;F:\JAVA\Maven\Repository\org\apache\tomcat\embed\tomcat-embed-websocket\9.0.41\tomcat-embed-websocket-9.0.41.jar;F:\JAVA\Maven\Repository\org\springframework\spring-web\5.3.2\spring-web-5.3.2.jar;F:\JAVA\Maven\Repository\org\springframework\spring-beans\5.3.2\spring-beans-5.3.2.jar;F:\JAVA\Maven\Repository\org\springframework\spring-webmvc\5.3.2\spring-webmvc-5.3.2.jar;F:\JAVA\Maven\Repository\org\springframework\spring-aop\5.3.2\spring-aop-5.3.2.jar;F:\JAVA\Maven\Repository\org\springframework\spring-context\5.3.2\spring-context-5.3.2.jar;F:\JAVA\Maven\Repository\org\springframework\spring-expression\5.3.2\spring-expression-5.3.2.jar;F:\JAVA\Maven\Repository\org\projectlombok\lombok\1.18.16\lombok-1.18.16.jar;F:\JAVA\Maven\Repository\org\slf4j\slf4j-api\1.7.30\slf4j-api-1.7.30.jar;F:\JAVA\Maven\Repository\org\springframework\spring-core\5.3.2\spring-core-5.3.2.jar;F:\JAVA\Maven\Repository\org\springframework\spring-jcl\5.3.2\spring-jcl-5.3.2.jar" design.Application
  2. 类B 实现接口operation1 方法
  3. 类B 实现接口operation2方法
  4. 类B 实现接口operation3方法
  5. 类D 实现接口operation1 方法
  6. 类D 实现接口operation4方法
  7. 类D 实现接口operation5方法

方案二：

  1. 类A通过Interface1依赖B，类C通过Interface1依赖D，如果类A和类C对于Interface1来说不是最小接口的话，那么类B和类D就不必实现他们不需要的方法
  2. 将Interface1分解成几个独立的接口，将类A和类C分别和这几个接口建议依赖关系，也就是采用接口隔离原则即最小接口
  3. 将Interface1接口分解为3个接口

image.png

  1. public class Application {
  3.     public static void main(String[] args)  {
  5.         A a = new A();
  6.         a.depend1(new B());
  7.         a.depend2(new B());
  8.         a.depend3(new B());
  10.         C c = new C();
  11.         c.depend1(new D());
  12.         c.depend4(new D());
  13.         c.depend5(new D());
  14.     }
  15. }
  16. interface Interface1 {
  17.     void operation1();
  18. }
  19. interface Interface2 {
  20.     void operation2();
  21.     void operation3();
  22. }
  23. interface Interface3 {
  24.     void operation4();
  25.     void operation5();
  26. }
  28. class B implements Interface1,Interface2 {
  30.     @Override
  31.     public void operation1() {
  32.         System.out.println("类B 实现接口operation1 方法");
  33.     }
  35.     @Override
  36.     public void operation2() {
  37.         System.out.println("类B 实现接口operation2方法");
  39.     }
  41.     @Override
  42.     public void operation3() {
  43.         System.out.println("类B 实现接口operation3方法");
  45.     }
  46. }
  48. class D implements Interface1,Interface3 {
  50.     @Override
  51.     public void operation1() {
  52.         System.out.println("类D 实现接口operation1 方法");
  53.     }
  55.     @Override
  56.     public void operation4() {
  57.         System.out.println("类D 实现接口operation4方法");
  58.     }
  60.     @Override
  61.     public void operation5() {
  62.         System.out.println("类D 实现接口operation5方法");
  63.     }
  64. }
  65. class A {
  66.     public void depend1(Interface1 interface1){
  67.         interface1.operation1();
  68.     }
  69.     public void depend2(Interface2 interface2){
  70.         interface2.operation2();
  71.     }
  72.     public void depend3(Interface2 interface2){
  73.         interface2.operation3();
  74.     }
  76. }
  77. class C {
  78.     public void depend1(Interface1 interface1){
  79.         interface1.operation1();
  80.     }
  81.     public void depend4(Interface3 interface3){
  82.         interface3.operation4();
  83.     }
  84.     public void depend5(Interface3 interface3){
  85.         interface3.operation5();
  86.     }
  88. }

运行结果：

  1. "F:\Program Files\Java\jdk1.8.0_201\bin\java.exe" "-javaagent:F:\Program Files\JetBrains\IntelliJ IDEA 2018.3\lib\idea_rt.jar=51009:F:\Program Files\JetBrains\IntelliJ IDEA 2018.3\bin" -Dfile.encoding=UTF-8 -classpath "F:\Program Files\Java\jdk1.8.0_201\jre\lib\charsets.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\deploy.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\access-bridge-64.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\cldrdata.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\dnsns.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\jaccess.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\jfxrt.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\localedata.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\nashorn.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunec.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunjce_provider.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunmscapi.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\sunpkcs11.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\ext\zipfs.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\javaws.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\jce.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\jfr.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\jfxswt.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\jsse.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\management-agent.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\plugin.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\resources.jar;F:\Program Files\Java\jdk1.8.0_201\jre\lib\rt.jar;E:\study\study_jvm\target\classes;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot-starter-web\2.4.1\spring-boot-starter-web-2.4.1.jar;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot-starter\2.4.1\spring-boot-starter-2.4.1.jar;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot\2.4.1\spring-boot-2.4.1.jar;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot-autoconfigure\2.4.1\spring-boot-autoconfigure-2.4.1.jar;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot-starter-logging\2.4.1\spring-boot-starter-logging-2.4.1.jar;F:\JAVA\Maven\Repository\ch\qos\logback\logback-classic\1.2.3\logback-classic-1.2.3.jar;F:\JAVA\Maven\Repository\ch\qos\logback\logback-core\1.2.3\logback-core-1.2.3.jar;F:\JAVA\Maven\Repository\org\apache\logging\log4j\log4j-to-slf4j\2.13.3\log4j-to-slf4j-2.13.3.jar;F:\JAVA\Maven\Repository\org\apache\logging\log4j\log4j-api\2.13.3\log4j-api-2.13.3.jar;F:\JAVA\Maven\Repository\org\slf4j\jul-to-slf4j\1.7.30\jul-to-slf4j-1.7.30.jar;F:\JAVA\Maven\Repository\jakarta\annotation\jakarta.annotation-api\1.3.5\jakarta.annotation-api-1.3.5.jar;F:\JAVA\Maven\Repository\org\yaml\snakeyaml\1.27\snakeyaml-1.27.jar;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot-starter-json\2.4.1\spring-boot-starter-json-2.4.1.jar;F:\JAVA\Maven\Repository\com\fasterxml\jackson\core\jackson-databind\2.11.3\jackson-databind-2.11.3.jar;F:\JAVA\Maven\Repository\com\fasterxml\jackson\core\jackson-annotations\2.11.3\jackson-annotations-2.11.3.jar;F:\JAVA\Maven\Repository\com\fasterxml\jackson\core\jackson-core\2.11.3\jackson-core-2.11.3.jar;F:\JAVA\Maven\Repository\com\fasterxml\jackson\datatype\jackson-datatype-jdk8\2.11.3\jackson-datatype-jdk8-2.11.3.jar;F:\JAVA\Maven\Repository\com\fasterxml\jackson\datatype\jackson-datatype-jsr310\2.11.3\jackson-datatype-jsr310-2.11.3.jar;F:\JAVA\Maven\Repository\com\fasterxml\jackson\module\jackson-module-parameter-names\2.11.3\jackson-module-parameter-names-2.11.3.jar;F:\JAVA\Maven\Repository\org\springframework\boot\spring-boot-starter-tomcat\2.4.1\spring-boot-starter-tomcat-2.4.1.jar;F:\JAVA\Maven\Repository\org\apache\tomcat\embed\tomcat-embed-core\9.0.41\tomcat-embed-core-9.0.41.jar;F:\JAVA\Maven\Repository\org\glassfish\jakarta.el\3.0.3\jakarta.el-3.0.3.jar;F:\JAVA\Maven\Repository\org\apache\tomcat\embed\tomcat-embed-websocket\9.0.41\tomcat-embed-websocket-9.0.41.jar;F:\JAVA\Maven\Repository\org\springframework\spring-web\5.3.2\spring-web-5.3.2.jar;F:\JAVA\Maven\Repository\org\springframework\spring-beans\5.3.2\spring-beans-5.3.2.jar;F:\JAVA\Maven\Repository\org\springframework\spring-webmvc\5.3.2\spring-webmvc-5.3.2.jar;F:\JAVA\Maven\Repository\org\springframework\spring-aop\5.3.2\spring-aop-5.3.2.jar;F:\JAVA\Maven\Repository\org\springframework\spring-context\5.3.2\spring-context-5.3.2.jar;F:\JAVA\Maven\Repository\org\springframework\spring-expression\5.3.2\spring-expression-5.3.2.jar;F:\JAVA\Maven\Repository\org\projectlombok\lombok\1.18.16\lombok-1.18.16.jar;F:\JAVA\Maven\Repository\org\slf4j\slf4j-api\1.7.30\slf4j-api-1.7.30.jar;F:\JAVA\Maven\Repository\org\springframework\spring-core\5.3.2\spring-core-5.3.2.jar;F:\JAVA\Maven\Repository\org\springframework\spring-jcl\5.3.2\spring-jcl-5.3.2.jar" design.Application
  2. 类B 实现接口operation1 方法
  3. 类B 实现接口operation2方法
  4. 类B 实现接口operation3方法
  5. 类D 实现接口operation1 方法
  6. 类D 实现接口operation4方法
  7. 类D 实现接口operation5方法