Initial commit

renren-common/src/main/java/io/renren/common/utils/TreeUtils.java

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+/**
+ * Copyright (c) 2018 人人开源 All rights reserved.
+ *
+ * https://www.renren.io
+ *
+ * 版权所有，侵权必究！
+ */
+
+package io.renren.common.utils;
+
+import io.renren.common.validator.AssertUtils;
+
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * 树形结构工具类，如：菜单、部门等
+ *
+ * @author Mark sunlightcs@gmail.com
+ * @since 1.0.0
+ */
+public class TreeUtils {
+
+    /**
+     * 根据pid，构建树节点
+     */
+    public static <T extends TreeNode> List<T> build(List<T> treeNodes, Long pid) {
+        //pid不能为空
+        AssertUtils.isNull(pid, "pid");
+
+        List<T> treeList = new ArrayList<>();
+        for(T treeNode : treeNodes) {
+            if (pid.equals(treeNode.getPid())) {
+                treeList.add(findChildren(treeNodes, treeNode));
+            }
+        }
+
+        return treeList;
+    }
+
+    /**
+     * 查找子节点
+     */
+    private static <T extends TreeNode> T findChildren(List<T> treeNodes, T rootNode) {
+        for(T treeNode : treeNodes) {
+            if(rootNode.getId().equals(treeNode.getPid())) {
+                rootNode.getChildren().add(findChildren(treeNodes, treeNode));
+            }
+        }
+        return rootNode;
+    }
+
+    /**
+     * 构建树节点
+     */
+    public static <T extends TreeNode> List<T> build(List<T> treeNodes) {
+        List<T> result = new ArrayList<>();
+
+        //list转map
+        Map<Long, T> nodeMap = new LinkedHashMap<>(treeNodes.size());
+        for(T treeNode : treeNodes){
+            nodeMap.put(treeNode.getId(), treeNode);
+        }
+
+        for(T node : nodeMap.values()) {
+            T parent = nodeMap.get(node.getPid());
+            if(parent != null && !(node.getId().equals(parent.getId()))){
+                parent.getChildren().add(node);
+                continue;
+            }
+
+            result.add(node);
+        }
+
+        return result;
+    }
+
+}