Composite组合模式

最新推荐文章于 2022-01-25 09:20:57 发布

原创最新推荐文章于 2022-01-25 09:20:57 发布 · 352 阅读

0 ·

CC 4.0 BY-SA版权

设计模式专栏收录该内容

21 篇文章

订阅专栏

本文深入探讨了软件工程中的组合模式，通过Java代码示例展示了如何使用该模式构建树状结构来表示部分-整体层次关系，使得客户端可以统一处理单个对象和组合。

文章目录

定义

In software engineering, the composite pattern is a partitioning design pattern. The composite pattern describes a group of objects that are treated the same way as a single instance of the same type of object. The intent of a composite is to “compose” objects into tree structures to represent part-whole hierarchies. Implementing the composite pattern lets clients treat individual objects and compositions uniformly. —Wikipedia

结构

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-Pn2eiakW-1582554010549)(https://s3-us-west-2.amazonaws.com/secure.notion-static.com/fc26a8f2-54ad-4298-bd34-b10765f7bc82/Untitled.png)]

Demo

import java.util.ArrayList;
import java.util.List;

abstract class Node {
    abstract public void p();
}

class LeafNode extends Node {
    String content;
    public LeafNode(String content) {this.content = content;}

    @Override
    public void p() {
        System.out.println(content);
    }
}

class BranchNode extends Node {
    List<Node> nodes = new ArrayList<>();

    String name;
    public BranchNode(String name) {this.name = name;}

    @Override
    public void p() {
        System.out.println(name);
    }

    public void add(Node n) {
        nodes.add(n);
    }
}


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

        BranchNode root = new BranchNode("root");
        BranchNode chapter1 = new BranchNode("chapter1");
        BranchNode chapter2 = new BranchNode("chapter2");
        Node r1 = new LeafNode("r1");
        Node c11 = new LeafNode("c11");
        Node c12 = new LeafNode("c12");
        BranchNode b21 = new BranchNode("section21");
        Node c211 = new LeafNode("c211");
        Node c212 = new LeafNode("c212");

        root.add(chapter1);
        root.add(chapter2);
        root.add(r1);
        chapter1.add(c11);
        chapter1.add(c12);
        chapter2.add(b21);
        b21.add(c211);
        b21.add(c212);
        //递归打印树
        tree(root, 0);

    }

    static void tree(Node b, int depth) {
        //每进一层，则多打印一个'-'
        for(int i=0; i<depth; i++) System.out.print("-");
        b.p();

        if(b instanceof BranchNode) {
            for (Node n : ((BranchNode)b).nodes) {
                tree(n, depth + 1);
            }
        }
    }
}

输出:

root
-chapter1
--c11
--c12
-chapter2
--section21
---c211
---c212
-r1

总结

树状结构 - 组合模式