组合模式

组合模式(Composite Pattern)使得用户对单个对象和组合对象的使用具有唯一性。

将对象组合成树形结构以表示【部分-整体】的层次结构。

实际案例

类信息概览：

类名 说明
Main.java 方法的总入口
Component.java 组件
Composite.java 组合类
Leaf.java 叶子

定义

  • Component.java
package com.ryo.design.pattern.note.composite;

/**
 *
 * @author bbhou
 * @date 2017/8/11
 */
public abstract class Component {

    private String name;

    public Component(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }

    /**
     * add one compoent
     * @param component
     */
    public abstract void add(Component component);

    /**
     * remove one compoent
     * @param component
     */
    public abstract void remove(Component component);

    /**
     * display the component info;
     * @param depth
     */
    public abstract void display(int depth);


}
  • Composite.java
package com.ryo.design.pattern.note.composite;

import java.util.LinkedList;
import java.util.List;

/**
 *
 * @author bbhou
 * @date 2017/8/11
 */
public class Composite extends Component {
    /**
     * 用于存放子节点
     */
    private List<Component> children = new LinkedList<>();

    /**
     * 定义枝节点行为，用来存储子部件，在 Component 接口中实现与子部件相关的操作。
     * @param name
     */
    public Composite(String name) {
        super(name);
    }

    @Override
    public void add(Component component) {
        this.children.add(component);
    }

    @Override
    public void remove(Component component) {
        this.children.remove(component);
    }

    @Override
    public void display(int depth) {
        //1.itself
        StringBuilder stringBuilder = new StringBuilder();
        for(int i = 0; i < depth; i++) {
            stringBuilder.append("-");
        }
        System.out.println(stringBuilder.toString()+" "+getName());

        //2.children
        for(Component component : this.children) {
            component.display(depth+2);
        }
    }
}
  • Leaf.java
package com.ryo.design.pattern.note.composite;

/**
 *
 * @author bbhou
 * @date 2017/8/11
 */
public class Leaf extends Component {

    public Leaf(String name) {
        super(name);
    }

    @Override
    public void add(Component component) {
        System.out.println("can't add child to leaf.");
    }

    @Override
    public void remove(Component component) {
        System.out.println("can't remove child from leaf.");
    }

    @Override
    public void display(int depth) {
        StringBuilder stringBuilder = new StringBuilder();
        for(int i = 0; i < depth; i++) {
            stringBuilder.append("-");
        }

        System.out.println(stringBuilder.toString()+" "+getName());
    }
}

测试

  • Main.java
/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * Copyright (c) 2012-2018. houbinbini Inc.
 * design-pattern All rights reserved.
 */

package com.ryo.design.pattern.note.composite;

/**
 * <p> </p>
 *
 * <pre> Created: 2018/5/16 下午8:11  </pre>
 * <pre> Project: design-pattern  </pre>
 *
 * @author houbinbin
 * @version 1.0
 * @since JDK 1.7
 */
public class Main {

    public static void main(String[] args) {
        Composite root = new Composite("root");
        root.add(new Leaf("Leaf A"));
        root.add(new Leaf("Leaf B"));

        Composite compX = new Composite("Composite X");
        compX.add(new Leaf("Leaf XA"));
        compX.add(new Leaf("Leaf XB"));
        root.add(compX);

        Composite compXY = new Composite("Composite XY");
        compXY.add(new Leaf("Leaf XYA"));
        compXY.add(new Leaf("Leaf XYB"));
        compX.add(compXY);

        root.display(1);
    }

}
  • 测试结果
- root
--- Leaf A
--- Leaf B
--- Composite X
----- Leaf XA
----- Leaf XB
----- Composite XY
------- Leaf XYA
------- Leaf XYB

实现方式

UML & Code

UML

UML 图示如下

Code

代码地址

组合模式

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