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 buildListToTree(List dirs) { 
        List roots = findRoots(dirs); 
        List notRoots = (List) 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 findRoots(List allNodes) { 
        List results = new ArrayList(); 
        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 findChildren(Node root, List allNodes) { 
        List children = new ArrayList(); 

        for (Node comparedOne : allNodes) { 
            if (comparedOne.getParentId() == root.getId()) { 
                comparedOne.setParent(root); 
                comparedOne.setLevel(root.getLevel() + 1); 
                children.add(comparedOne); 
            } 
        } 
        List notChildren = (List) CollectionUtils.subtract(allNodes, children); 
        for (Node child : children) { 
            List 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 allNodes = new ArrayList(); 
        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 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 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 getChildren() { 
return children; 
} 

public void setChildren(List 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 + "}"; 
} 
}