add recursive path find demo

add demo for creating new thred

src/recursive/TreeStructure.java

@@ -0,0 +1,42 @@
+package recursive;
+
+import java.util.*;
+
+public class TreeStructure {
+
+    public static void main(String[] args) {
+        List<TreeNode> treeNodes = new ArrayList<>();
+        Set<Integer> leafSet = new HashSet<>();
+        treeNodes.add(new TreeNode(1,0,"root"));
+        treeNodes.add(new TreeNode(2,1,"a1"));
+        treeNodes.add(new TreeNode(3,1,"a2"));
+        treeNodes.add(new TreeNode(4,2,"b1"));
+        treeNodes.add(new TreeNode(5,4,"c1"));
+
+        Map<Integer, TreeNode> treeMap = new HashMap<>();
+
+        for (TreeNode treeNode : treeNodes) {
+            leafSet.add(treeNode.getId());
+        }
+
+        for (TreeNode treeNode : treeNodes) {
+            treeMap.put(treeNode.getId(), treeNode);
+            leafSet.remove(treeNode.getParentId());
+        }
+
+        for (Integer id: leafSet) {
+            int parentId = treeMap.get(id).getParentId();
+            int nodeId = id;
+            while (parentId != 0) {
+                treeMap.get(parentId).addChild(treeMap.get(nodeId));
+                nodeId = parentId;
+                parentId = treeMap.get(nodeId).getParentId();
+            }
+        }
+
+        TreeNode finalNode = treeMap.values().stream()
+                .filter(treeNode -> treeNode.getParentId() == 0).toList().getFirst();
+
+        System.out.println(finalNode);
+    }
+}