組合模式(Composite) : 組合模式有時又叫部分-整體模式在處理類似樹形結構的問題時比較方便
使用場景：將多個對象組合在一起進行操作，常用于表示樹形結構中

作者是個二吊子,如果描述有誤請指出.

目錄

• 使用場景
• 組合模式

使用場景

我們可能會操作到一些屬性結構的數據,常見的是省市區,多級菜單.它們會具有較多的類似行為(方法).在這個時候我們常見的操作是進行多級菜單定義或者通用一個類來做.如果進行多級菜單定義可能會導致類爆炸.通用一個類的話就可能是靈活度不高,比如有少數方法的差異性處理是做不到的.后期擴展會很麻煩.以此引出組合模式.

組合模式

uml圖

這里我們用大學,學院,系來進行距離,網上通用模板
OrganizationComponent : 抽象接口,提供公共的操作方法,用于訪問和管理子部件
Department: 葉子結點,沒有子節點了,作為最底層
College,University: 容器對象義有枝節點行為，用來存儲子部件，在OrganizationComponent 接口中實現與子部件通用操作

/**
 * @Description: 抽象類根級
 * @Author: gaofan
 * @Date: 2020/3/23 13:52
 * @Copyright: 2020 www.withu.top Inc. All rights reserved.
 **/
public abstract class OrganizationComponent {

    private String name;

    private String desc;

    protected void add(OrganizationComponent organizationComponent) {
        throw new UnsupportedOperationException("不支持操作");
    }

    protected void remove(OrganizationComponent organizationComponent) {
        throw new UnsupportedOperationException("不支持操作");
    }

    protected abstract void print();

    public OrganizationComponent(String name, String desc) {
        this.name = name;
        this.desc = desc;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }
}

/**
 * @Description: 學院,容器對象-非葉子節點
 * @Author: gaofan
 * @Date: 2020/3/23 14:02
 * @Copyright: 2020 www.withu.top Inc. All rights reserved.
 **/
public class College extends OrganizationComponent{

    List<OrganizationComponent> organizationComponentList = new ArrayList<>();

    public College(String name, String desc) {
        super(name, desc);
    }

    @Override
    protected void add(OrganizationComponent organizationComponent) {
        organizationComponentList.add(organizationComponent);
    }

    @Override
    protected void remove(OrganizationComponent organizationComponent) {
        organizationComponentList.remove(organizationComponent);
    }

    @Override
    protected void print() {
        System.out.println("-------次頂層--------"+getName() + "------------");
        for(OrganizationComponent organizationComponent: organizationComponentList){
            organizationComponent.print();
        }
    }
}

/**
 * @Description: 大學,容器對象-非葉子節點
 * @Author: gaofan
 * @Date: 2020/3/23 13:56
 * @Copyright: 2020 www.withu.top Inc. All rights reserved.
 **/
public class University extends OrganizationComponent {

    List<OrganizationComponent> organizationComponentList = new ArrayList<>();

    public University(String name, String desc) {
        super(name, desc);
    }

    @Override
    protected void add(OrganizationComponent organizationComponent) {
        organizationComponentList.add(organizationComponent);
    }

    @Override
    protected void remove(OrganizationComponent organizationComponent) {
        organizationComponentList.remove(organizationComponent);
    }

    @Override
    protected void print() {
        System.out.println("-------頂層--------"+getName() + "------------");
        for(OrganizationComponent organizationComponent: organizationComponentList){
            organizationComponent.print();
        }
    }
}

/**
 * @Description: 系
 * @Author: gaofan
 * @Date: 2020/3/23 14:05
 * @Copyright: 2020 www.withu.top Inc. All rights reserved.
 **/
public class Department extends OrganizationComponent {

    public Department(String name, String desc) {
        super(name, desc);
    }

    @Override
    public String getName() {
        return super.getName();
    }

    @Override
    public String getDesc() {
        return super.getDesc();
    }

    @Override
    protected void print() {
        System.out.println("----葉子節點--------"+getName() + "------------");
    }
}

/**
 * @Description: TODO
 * @Author: gaofan
 * @Date: 2020/3/23 14:07
 * @Copyright: 2020 www.withu.top Inc. All rights reserved.
 **/
public class Client {

    public static void main(String [] args){
        OrganizationComponent university = new University("宜賓學院", "中國次頂級學校");

        OrganizationComponent college = new College("物理與電子工程學院","老學院");

        OrganizationComponent college1 = new College("經管學院","新學院");

        college.add(new Department("電子信息工程","還行"));
        college.add(new Department("物理系","不錯"));
        college1.add(new Department("國際貿易","一般"));
        college1.add(new Department("財經貿易","不知道"));
        university.add(college);
        university.add(college1);
        university.print();
    }
}

類型: 組合模式
原理: 樹形結構具有較多通用方法時可用于此類.減少使用繼承的手法之一.通過定義接口或者抽象類對容器對象,葉子對象行為(方法)進行抽象,可根據各自行為自行實現(差異化).容器對象通過組合的方式持有容器對象或者葉子對象.對其進行操作.
優點: 減少耦合性,復用性增強,靈活性較強

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