利用Map把一维数据转换成树结构

工具类：

import java.util.ArrayList;import java.util.LinkedHashMap;import java.util.List;import java.util.Map;public class AssmTreeUtil {public static List<TreeNode> assmTree(List<TreeNode> singleTreeNodes) {if(singleTreeNodes == null || singleTreeNodes.isEmpty()) {return null;}List<TreeNode> nodeTrees = new ArrayList<TreeNode>();Map<String,TreeNode> treeMap = new LinkedHashMap<String,TreeNode>();for(TreeNode node : singleTreeNodes){TreeNode treeNode = new TreeNode();treeNode.setNodeId(node.getNodeId());treeNode.setNodeName(node.getNodeName());treeNode.setPid(node.getPid());treeMap.put(node.getNodeId(), treeNode);}for(String nodeId : treeMap.keySet()){TreeNode treeNode = treeMap.get(nodeId);String pid = treeNode.getPid();if(pid==null || pid.length()==0 || !treeMap.containsKey(pid)){treeNode.setPid("");nodeTrees.add(treeNode);}else{TreeNode parentTreeNode = treeMap.get(pid);if(parentTreeNode.getChildren()==null){parentTreeNode.setChildren(new ArrayList<TreeNode>());}parentTreeNode.getChildren().add(treeNode);}}return nodeTrees;}}

bean类：

import java.util.List;public class TreeNode {/** * 父节点ID */private String pid;/** * 节点ID */private String nodeId;/** * 节点名称 */private String nodeName;/** * 子节点 */private List<TreeNode> children;public String getPid() {return pid;}public void setPid(String pid) {this.pid = pid;}public String getNodeId() {return nodeId;}public void setNodeId(String nodeId) {this.nodeId = nodeId;}public String getNodeName() {return nodeName;}public void setNodeName(String nodeName) {this.nodeName = nodeName;}public List<TreeNode> getChildren() {return children;}public void setChildren(List<TreeNode> children) {this.children = children;}}

小结：实现相关功能的，网上也有其它例子，但都是用多个ArrayList的，代码比较长。利用LinkedHashMap能更好的实现。