2 接口隔离原则

客户端不应该依赖它不需要的接口，即一个类对另一个类的依赖应该建立在最小的接口上

优化前：

//接口
interface Interface1 {
   void operation1();
   void operation2();
   void operation3();
   void operation4();
   void operation5();
}
class B implements Interface1 {
   public void operation1() {
      System.out.println("B 实现了 operation1");
   }
   public void operation2() {
      System.out.println("B 实现了 operation2");
   }
   public void operation3() {
      System.out.println("B 实现了 operation3");
   }
   public void operation4() {
      System.out.println("B 实现了 operation4");
   }
   public void operation5() {
      System.out.println("B 实现了 operation5");
   }
}
class D implements Interface1 {
   public void operation1() {
      System.out.println("D 实现了 operation1");
   }
   public void operation2() {
      System.out.println("D 实现了 operation2");
   }
   public void operation3() {
      System.out.println("D 实现了 operation3");
   }
   public void operation4() {
      System.out.println("D 实现了 operation4");
   }
   public void operation5() {
      System.out.println("D 实现了 operation5");
   }
}
class A { //A 类通过接口Interface1 依赖(使用) B类，但是只会用到1,2,3方法
   public void depend1(Interface1 i) {
      i.operation1();
   }
   public void depend2(Interface1 i) {
      i.operation2();
   }
   public void depend3(Interface1 i) {
      i.operation3();
   }
}
class C { //C 类通过接口Interface1 依赖(使用) D类，但是只会用到1,4,5方法
   public void depend1(Interface1 i) {
      i.operation1();
   }
   public void depend4(Interface1 i) {
      i.operation4();
   }
   public void depend5(Interface1 i) {
      i.operation5();
   }
}

_

优化后：

优化后

interface Interface1 {
    void operation1();
}
// 接口2
interface Interface2 {
    void operation2();
    void operation3();
}
// 接口3
interface Interface3 {
    void operation4();
    void operation5();
}
class B implements Interface1, Interface2 {
    public void operation1() {
        System.out.println("B 实现了 operation1");
    }
    public void operation2() {
        System.out.println("B 实现了 operation2");
    }
    public void operation3() {
        System.out.println("B 实现了 operation3");
    }
}
class D implements Interface1, Interface3 {
    public void operation1() {
        System.out.println("D 实现了 operation1");
    }
    public void operation4() {
        System.out.println("D 实现了 operation4");
    }
    public void operation5() {
        System.out.println("D 实现了 operation5");
    }
}
class A { // A 类通过接口Interface1,Interface2 依赖(使用) B类，但是只会用到1,2,3方法
    public void depend1(Interface1 i) {
        i.operation1();
    }
    public void depend2(Interface2 i) {
        i.operation2();
    }
    public void depend3(Interface2 i) {
        i.operation3();
    }
}
class C { // C 类通过接口Interface1,Interface3 依赖(使用) D类，但是只会用到1,4,5方法
    public void depend1(Interface1 i) {
        i.operation1();
    }
    public void depend4(Interface3 i) {
        i.operation4();
    }
    public void depend5(Interface3 i) {
        i.operation5();
    }
}

java