java对于树的构建

package tree;

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

import org.apache.commons.collections.CollectionUtils;


public class TreeBuilder {

    /**
     * 将集合建立成树结构
     *
     * @param dirs
     * @return
     */
    @SuppressWarnings("unchecked")
    private List<Node> buildListToTree(List<Node> dirs) {
        List<Node> roots = findRoots(dirs);
        List<Node> notRoots = (List<Node>) CollectionUtils.subtract(dirs, roots);
        for (Node root : roots) {
            root.setChildren(findChildren(root, notRoots));
        }
        return roots;
    }

    /**
     * 找出集合中的根元素
     *
     * @param allDirs
     * @return
     */
    public List<Node> findRoots(List<Node> allNodes) {
        List<Node> results = new ArrayList<Node>();
        for (Node node : allNodes) {
            boolean isRoot = true;
            for (Node comparedOne : allNodes) {
                if (node.getParentId() == comparedOne.getId()) {
                    isRoot = false;
                    break;
                }
            }
            if (isRoot) {
                node.setLevel(0);
                results.add(node);
                node.setRootId(node.getId());
            }
        }
        return results;
    }

    /**
     * 递归找子目录
     *
     * @param root
     * @param allDirs
     * @return
     */
    @SuppressWarnings("unchecked")
    private List<Node> findChildren(Node root, List<Node> allNodes) {
        List<Node> children = new ArrayList<Node>();

        for (Node comparedOne : allNodes) {
            if (comparedOne.getParentId() == root.getId()) {
                comparedOne.setParent(root);
                comparedOne.setLevel(root.getLevel() + 1);
                children.add(comparedOne);
            }
        }
        List<Node> notChildren = (List<Node>) CollectionUtils.subtract(allNodes, children);
        for (Node child : children) {
            List<Node> tmpChildren = findChildren(child, notChildren);
            if (tmpChildren == null || tmpChildren.size() < 1) {
                child.setLeaf(true);
            } else {
                child.setLeaf(false);
            }
            child.setChildren(tmpChildren);
        }
        return children;
    }

    public static void main(String[] args) {
        TreeBuilder tb = new TreeBuilder();
        List<Node> allNodes = new ArrayList<Node>();
        allNodes.add(new Node(1,0,"节点1"));
        allNodes.add(new Node(2,0,"节点2"));
        allNodes.add(new Node(3,0,"节点3"));
        allNodes.add(new Node(4,1,"节点4"));
        allNodes.add(new Node(5,1,"节点5"));
        allNodes.add(new Node(6,1,"节点6"));
        allNodes.add(new Node(7,4,"节点7"));
        allNodes.add(new Node(8,4,"节点8"));
        allNodes.add(new Node(9,5,"节点9"));
        allNodes.add(new Node(10,100,"节点10"));
        List<Node> roots = tb.buildListToTree(allNodes);
        for(Node n:roots){
            System.out.println(n);
        }

    }
}






package tree;

import java.util.List;

public class Node implements java.io.Serializable {
private static final long serialVersionUID = -2721191232926604726L;

private int id;

private int parentId;

private Node parent;

private List<Node> children;

private String name;

private int level;

private int sort;

private int rootId;

private String type;

private boolean isLeaf;

private String description;


public Node() {
super();
}

public Node(int id, int parentId, String name) {
super();
this.id = id;
this.parentId = parentId;
this.name = name;
}


public String getDescription() {
return description;
}

public void setDescription(String description) {
this.description = description;
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public Node getParent() {
return parent;
}

public void setParent(Node parent) {
this.parent = parent;
}

public int getParentId() {
return parentId;
}

public void setParentId(int parentId) {
this.parentId = parentId;
}

public String getName() {
return name;
}

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

public int getLevel() {
return level;
}

public void setLevel(int level) {
this.level = level;
}

public String getType() {
return type;
}

public List<Node> getChildren() {
return children;
}

public void setChildren(List<Node> children) {
this.children = children;
}

public void setType(String type) {
this.type = type;
}

public boolean isLeaf() {
return isLeaf;
}

public void setLeaf(boolean isLeaf) {
this.isLeaf = isLeaf;
}

public int getSort() {
return sort;
}

public void setSort(int sort) {
this.sort = sort;
}



public int getRootId() {
        return rootId;
    }

public void setRootId(int rootId) {
        this.rootId = rootId;
    }








    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + id;
        result = prime * result + parentId;
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Node other = (Node) obj;
        if (id != other.id)
            return false;
        if (parentId != other.parentId)
            return false;
        return true;
    }

    @Override
public String toString() {
return "Node {id=" + id + ", parentId=" + parentId
+ ", children=" + children + ", name=" + name + "}";
}
}