组合模式（结构型）

 

设计模式的3个分类：创建型模式、结构型模式、行为型模式

 

组合模式定义：

组合模式，又叫部分整体模式，是指将对象组合成树形结构以表示“部分-整体”的层次结构，组合模式使得对象对单个对象和组合对象对使用具有一致性（把一组相似的对象当作一个单一的对象）。

 

组合模式图示：

 

 

代码实现：

/**
 * 这里也可以是接口（根据实际问题来）
 */
public abstract class OrganizationComponent {

    private String name;
    private String des;

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

    public String getName() {
        return name;
    }

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

    public String getDes() {
        return des;
    }

    public void setDes(String des) {
        this.des = des;
    }

    //不抽象(因为有叶子节点)
    protected void add(OrganizationComponent organizationComponent) {
        //默认实现
        throw new UnsupportedOperationException();
    }

    protected void remove(OrganizationComponent organizationComponent) {
        //默认实现
        throw new UnsupportedOperationException();
    }

    //打印（抽象方法）
    protected abstract void print();
    
}

//类似树的根节点
public class University extends OrganizationComponent {

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

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

    //重写add
    @Override
    protected void add(OrganizationComponent organizationComponent) {
        organizationComponents.add(organizationComponent);
    }

    //重写remove
    @Override
    protected void remove(OrganizationComponent organizationComponent) {
        organizationComponents.remove(organizationComponent);
    }


    //print方法，输出University包含的学院
    @Override
    protected void print() {
        System.out.println("----------------------" + getName() + "----------------------");
        for (OrganizationComponent oc : organizationComponents) {
            oc.print();
        }
    }
}

//类似树的中间节点
public class College extends OrganizationComponent{

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

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

    //重写add
    @Override
    protected void add(OrganizationComponent organizationComponent) {
        organizationComponents.add(organizationComponent);
    }

    //重写remove
    @Override
    protected void remove(OrganizationComponent organizationComponent) {
        organizationComponents.remove(organizationComponent);
    }


    //print方法，输出College包含的系
    @Override
    protected void print() {
        System.out.println("------------" + getName() + "------------");
        for (OrganizationComponent oc : organizationComponents) {
            oc.print();
        }
    }
}

//类似树的叶子节点
public class Department extends OrganizationComponent{

    //叶子节点，这里面不再有集合
    public Department(String name, String des) {
        super(name, des);
    }

    @Override
    protected void print() {
        System.out.println(getName());
    }
}

/**
 * 组合模式
 */
public class CompositePatternDemo {

    public static void main(String[] args) {


        //create university
        OrganizationComponent university = new University("Tsinghua University", "Top University");

        //create college
        OrganizationComponent computerCollege = new College("计算机学院", "学院000");
        OrganizationComponent infoEngineerCollege = new College("信息工程学院", "学院111");

        //create department and add to college
        computerCollege.add(new Department("软件工程", "AAA"));
        computerCollege.add(new Department("网络工程", "BBB"));
        computerCollege.add(new Department("计算机科学与技术", "CCC"));

        //create department and add to college
        infoEngineerCollege.add(new Department("通信工程", "DDD"));
        infoEngineerCollege.add(new Department("信息工程", "EEE"));

        //add college to university
        university.add(computerCollege);
        university.add(infoEngineerCollege);

        university.print();
//        computerCollege.print();
//        infoEngineerCollege.print();
    }
}

　　

应用：

在Java中，Map、HashMap的使用是运用了“组合模式”；

在实际的开发中，可以结合实际情况，进行抽象类或接口的设计（非必须），进而使用组合模式。