接口隔离原则

定义：客户端不应该被迫依赖于它不使用的方法，即：一个类对另一个类的依赖应该建立在最小的接口上

以安全门为例：

存在的问题：如果要增加新的品牌的安全门，则违背了开闭原则

SafetyDoor

public interface SafetyDoor {

    /**
     * 防盗
     */
    void antiTheft();

    /**
     * 防火
     */
    void fireproof();

    /**
     * 防水
     */
    void waterproof();
}

TestSafetyDoor

public class TestSafetyDoor implements SafetyDoor {
    @Override
    public void antiTheft() {
        System.out.println("防盗");
    }

    @Override
    public void fireproof() {
        System.out.println("防火");
    }

    @Override
    public void waterproof() {
        System.out.println("防水");
    }
}

Client

public class Client {
    public static void main(String[] args) {
        //存在的问题：如果要增加新的品牌的安全门，则违背了开闭原则
        TestSafetyDoor testSafetyDoor = new TestSafetyDoor();
        testSafetyDoor.antiTheft();
        testSafetyDoor.fireproof();
        testSafetyDoor.waterproof();
    }
}

改进：

抽象出安全门各个功能的接口，新增其他品牌的安全门时只需实现对应功能的接口

AntiTheft

public interface AntiTheft {

    /**
     * 防盗
     */
    void antiTheft();
}

Fireproof

public interface Fireproof {

    /**
     * 防火
     */
    void fireproof();
}

Waterproof

public interface Waterproof {

    /**
     * 防水
     */
    void waterproof();
}

TestSafetyDoor

public class TestSafetyDoor implements AntiTheft, Fireproof, Waterproof {

    @Override
    public void antiTheft() {
        System.out.println("防盗");
    }

    @Override
    public void fireproof() {
        System.out.println("防火");
    }

    @Override
    public void waterproof() {
        System.out.println("防水");
    }
}

Test01SafetyDoor

public class Test01SafetyDoor implements AntiTheft, Fireproof {

    @Override
    public void antiTheft() {
        System.out.println("防盗");
    }

    @Override
    public void fireproof() {
        System.out.println("防火");
    }
}

Client

public class Client {
    public static void main(String[] args) {
        //Test品牌安全门
        TestSafetyDoor testSafetyDoor = new TestSafetyDoor();
        testSafetyDoor.antiTheft();
        testSafetyDoor.fireproof();
        testSafetyDoor.waterproof();

        System.out.println("=================");

        //Test品牌安全门
        Test01SafetyDoor test01SafetyDoor = new Test01SafetyDoor();
        test01SafetyDoor.antiTheft();
        test01SafetyDoor.fireproof();
    }
}