1. 概念

客戶端不應(yīng)該依賴它不需要的接口，即一個(gè)類對(duì)另一個(gè)類的依賴應(yīng)該建立在最小的接口上

2. 代碼示例

示例1

• 在示例1中不滿足接口隔離原則
• Interface1接口的部分方法A、B類是不需要用到的，但對(duì)A、B類是可見的

public class S1 {
    public static void main(String[] args) {

    }
}

interface Interface01 {
    void operation01();

    void operation02();

    void operation03();

    void operation04();

    void operation05();
}

class B implements Interface01 {
    @Override
    public void operation01() {
        System.out.println("B 實(shí)現(xiàn)了 operation01");
    }

    @Override
    public void operation02() {
        System.out.println("B 實(shí)現(xiàn)了 operation02");
    }

    @Override
    public void operation03() {
        System.out.println("B 實(shí)現(xiàn)了 operation03");
    }

    @Override
    public void operation04() {
        System.out.println("B 實(shí)現(xiàn)了 operation04");
    }

    @Override
    public void operation05() {
        System.out.println("B 實(shí)現(xiàn)了 operation05");
    }
}

class D implements Interface01 {
    @Override
    public void operation01() {
        System.out.println("D 實(shí)現(xiàn)了 operation01");
    }

    @Override
    public void operation02() {
        System.out.println("D 實(shí)現(xiàn)了 operation02");
    }

    @Override
    public void operation03() {
        System.out.println("D 實(shí)現(xiàn)了 operation03");
    }

    @Override
    public void operation04() {
        System.out.println("D 實(shí)現(xiàn)了 operation04");
    }

    @Override
    public void operation05() {
        System.out.println("D 實(shí)現(xiàn)了 operation05");
    }
}

/**
 * A 類通過接口 Interface01 依賴 B類，但是只會(huì)用到 1,2,3方法
 */
class A {
    public void depend01(Interface01 interface01) {
        interface01.operation01();
    }
    public void depend02(Interface01 interface01) {
        interface01.operation02();
    }
    public void depend03(Interface01 interface01) {
        interface01.operation03();
    }
}
/**
 * C 類通過接口 Interface01 依賴 D類，但是只會(huì)用到 1,4,5方法
 */
class C {
    public void depend01(Interface01 interface01) {
        interface01.operation01();
    }
    public void depend04(Interface01 interface01) {
        interface01.operation04();
    }
    public void depend05(Interface01 interface01) {
        interface01.operation05();
    }
}

示例1-UML類圖

0223001.png

示例2

• 滿足接口隔離原則
• 將示例1中的接口Interface01，拆分成Interface001、Interface002、Interface003
• 在此示例2中AI、CI類中不需要的方法對(duì)其是不可見的，滿足接口隔離原則

/**
 * 接口隔離原則
 */
public class S2Improve {
    public static void main(String[] args) {
        AI ai = new AI();
        ai.depend01(new BI());
        ai.depend02(new BI());
        ai.depend03(new BI());

        CI ci = new CI();
        ci.depend01(new DI());
        ci.depend04(new DI());
        ci.depend05(new DI());
    }
}

interface Interface001 {
    void operation01();
}

interface Interface002 {
    void operation02();

    void operation03();
}

interface Interface003 {
    void operation04();

    void operation05();
}

class BI implements Interface001, Interface002 {
    @Override
    public void operation01() {
        System.out.println("B 實(shí)現(xiàn)了 operation01");
    }

    @Override
    public void operation02() {
        System.out.println("B 實(shí)現(xiàn)了 operation02");
    }

    @Override
    public void operation03() {
        System.out.println("B 實(shí)現(xiàn)了 operation03");
    }
}

class DI implements Interface001, Interface003 {
    @Override
    public void operation01() {
        System.out.println("D 實(shí)現(xiàn)了 operation01");
    }

    @Override
    public void operation04() {
        System.out.println("D 實(shí)現(xiàn)了 operation04");
    }

    @Override
    public void operation05() {
        System.out.println("D 實(shí)現(xiàn)了 operation05");
    }
}

/**
 * A 類通過接口 Interface001, Interface002 依賴 B類，但是只會(huì)用到 1,2,3方法
 */
class AI {
    public void depend01(Interface001 interface001) {
        interface001.operation01();
    }

    public void depend02(Interface002 interface002) {
        interface002.operation02();
    }

    public void depend03(Interface002 interface002) {
        interface002.operation03();
    }
}

/**
 * C 類通過接口 Interface001, Interface003 依賴 D類，但是只會(huì)用到 1,4,5方法
 */
class CI {
    public void depend01(Interface001 interface001) {
        interface001.operation01();
    }

    public void depend04(Interface003 interface003) {
        interface003.operation04();
    }

    public void depend05(Interface003 interface003) {
        interface003.operation05();
    }
}

示例2-UML類圖

0323002.png