组合模式

树：根节点只有子节点，没有父节点；叶子只有父节点，没有子节点，其他节点既有父节点也有子节点；

将数的节点抽象成一个接口，利用组合模式组装成树；

树节点接口：

package com.whereta.composite;

import java.util.List;

/**
 * Vincent 创建于 2016/4/26.
 */
public interface ITree {

    int count();

    String getName();

    void add(ITree tree);

    boolean hasParent();

    boolean isLeaf();

    ITree getParent();

    List<ITree> getChildren();
}

叶子实现：

package com.whereta.composite;

import java.util.List;

/**
 * Vincent 创建于 2016/4/26.
 */
public class Leaf implements ITree {

    private String name;

    private ITree parent;

    public Leaf(String name, ITree parent) {
        this.name = name;
        this.parent = parent;
    }

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

    public void add(ITree tree) {

    }

    public boolean hasParent() {
        return this.parent!=null;
    }

    public boolean isLeaf() {
        return true;
    }

    public ITree getParent() {
        return parent;
    }

    public List<ITree> getChildren() {
        return null;
    }

    public int count() {
        return 1;
    }
}

非叶子节点实现：

package com.whereta.composite;

import com.alibaba.fastjson.JSON;

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

/**
 * Vincent 创建于 2016/4/26.
 */
public class Trunk implements ITree {

    private String name;

    private ITree parent;

    private List<ITree> treeList = new ArrayList<ITree>();

    public Trunk(String name, ITree parent) {
        this.name = name;
        this.parent = parent;
    }

    public int count() {
        int num = 0;
        for (ITree tree : treeList) {
            num += tree.count();
        }
        return num;
    }

    public void add(ITree tree) {
        treeList.add(tree);
    }

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

    @Override
    public String toString() {
        return "Trunk{" +
                "name='" + name + '\'' +
                ", parent=" + com.alibaba.fastjson.JSON.toJSONString(parent) +
                ", treeList=" + JSON.toJSONString(treeList) +
                '}';
    }

    public boolean hasParent() {
        return this.parent!=null;
    }

    public boolean isLeaf() {
        return treeList.isEmpty();
    }

    public ITree getParent() {
        return parent;
    }

    public List<ITree> getChildren() {
        return treeList;
    }
}

测试：

package com.whereta.composite;

/**
 * Vincent 创建于 2016/4/26.
 */
public class Main {
    public static void main(String[] args) {
        ITree trunk=new Trunk("树干",null);

        ITree leaf1=new Leaf("叶子1",trunk);
        ITree leaf2=new Leaf("叶子2",trunk);
        ITree leaf3=new Leaf("叶子3",trunk);

        trunk.add(leaf1);
        trunk.add(leaf2);
        trunk.add(leaf3);

        System.out.println(trunk.toString());
    }
}

输出：

Trunk{name='树干', parent=null, treeList=[{"leaf":true,"name":"叶子1","parent":{"children":[{"$ref":"$[0]"},{"leaf":true,"name":"叶子2","parent":{"$ref":"$[0].parent"}},{"leaf":true,"name":"叶子3","parent":{"$ref":"$[0].parent"}}],"leaf":false,"name":"树干"}},{"$ref":"$[0].parent.children[1]"},{"$ref":"$[0].parent.children[2]"}]}

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