设计模式之接口分离原则

定义：

以上截图的uml图已添加注释，代码实现如下：

public class Segregation {
    public static void main(String[] args) {
        A a = new A();
        B b = new B();
        C c = new C();
        D d = new D();
        a.useInterface1(b);
        a.useInterface2(b);
        a.useInterface3(b);
        c.useInterface1(d);
        c.useInterface4(d);
        c.useInterface5(d);
    }
}

interface Interface1{
    void operation1();
    void operation2();
    void operation3();
    void operation4();
    void operation5();
}


class B implements Interface1{

    @Override
    public void operation1() {
        System.out.println("B实现operation1");
    }

    @Override
    public void operation2() {
        System.out.println("B实现operation2");
    }

    @Override
    public void operation3() {
        System.out.println("B实现operation3");
    }

    @Override
    public void operation4() {
        System.out.println("B实现operation4");
    }

    @Override
    public void operation5() {
        System.out.println("B实现operation5");
    }
}


class D implements Interface1{
    @Override
    public void operation1() {
        System.out.println("D实现operation1");
    }

    @Override
    public void operation2() {
        System.out.println("D实现operation2");
    }

    @Override
    public void operation3() {
        System.out.println("D实现operation3");
    }

    @Override
    public void operation4() {
        System.out.println("D实现operation4");
    }

    @Override
    public void operation5() {
        System.out.println("D实现operation5");
    }
}

class A {
    public void useInterface1(Interface1 interface1){
        interface1.operation1();
    }
    public void useInterface2(Interface1 interface1){
        interface1.operation2();
    }
    public void useInterface3(Interface1 interface1){
        interface1.operation3();
    }
}

class C {
    public void useInterface1(Interface1 interface1){
        interface1.operation1();
    }
    public void useInterface4(Interface1 interface1){
        interface1.operation4();
    }
    public void useInterface5(Interface1 interface1){
        interface1.operation5();
    }
}

以上代码的问题在于A类只是用接口中的1，2，3方法，C类只使用接口中的1，4、5方法。所以B类其实只要实现1，2，3方法。D类只要实现1，4，5方法。

 解决办法：

修改后的类图：

接口需要拆分成3个接口， 代码实现如下：

public class Segregation {
    public static void main(String[] args) {
        A a = new A();
        B b = new B();
        C c = new C();
        D d = new D();
        a.useInterface1(b);
        a.useInterface2(b);
        a.useInterface3(b);
        c.useInterface1(d);
        c.useInterface4(d);
        c.useInterface5(d);
    }
}

interface Interface1{
    void operation1();
}
interface Interface2 {
    void operation2();
    void operation3();
}
interface Interface3{
    void operation4();
    void operation5();
}
class B implements Interface1, Interface2{
    @Override
    public void operation1() {
        System.out.println("B实现operation1");
    }
    @Override
    public void operation2() {
        System.out.println("B实现operation2");
    }
    @Override
    public void operation3() {
        System.out.println("B实现operation3");
    }
}


class D implements Interface1, Interface3{
    @Override
    public void operation1() {
        System.out.println("D实现operation1");
    }
    @Override
    public void operation4() {
        System.out.println("D实现operation4");
    }
    @Override
    public void operation5() {
        System.out.println("D实现operation5");
    }
}

class A {
    public void useInterface1(Interface1 interface1){
        interface1.operation1();
    }
    public void useInterface2(Interface2 interface2){
        interface2.operation2();
    }
    public void useInterface3(Interface2 interface2){
        interface2.operation3();
    }
}

class C {
    public void useInterface1(Interface1 interface1){
        interface1.operation1();
    }
    public void useInterface4(Interface3 interface3){
        interface3.operation4();
    }
    public void useInterface5(Interface3 interface3){
        interface3.operation5();
    }
}