How to construct a n-ary tree from it's preorder traversal if the hierarchy levels are given

Main.java

build.gradle

How to construct a n-ary tree from it's preorder traversal if the hierarchy levels are given

Main.java

build.gradle

import org.json.JSONArray;
import org.json.JSONObject;

import java.util.Stack;

public class Main {

public static ResponseDTO getTreeStructure(JSONObject sapResponse) {
        JSONObject response = new JSONObject();
        Stack<JSONObject> treeStack = new Stack<>();
        JSONArray iteratingArray = sapResponse.getJSONArray("TONODES");

for (int i = 0; i < iteratingArray.length(); i++) {
            JSONObject tempObject = iteratingArray.getJSONObject(i);

if (treeStack.empty()) {
                //When the tree is empty the current node is put as the root
                response.put(tempObject.getString("Groupname"), tempObject);
                treeStack.push(tempObject);

//Checking if the current node is a child of the previous node (the one at the top of the stack)
            } else if (treeStack.peek().getInt("Hierlevel") < tempObject.getInt("Hierlevel")) {

// Retrieving the parent node from the stack with 'treeStack.peek()'
                // instead of retrieving it from the json (response) with 'response.getJSONObject(treeStack.peek().getString("Groupname"))'
                //
                // The previous writing couldn't work, because getJSONObject() searches for an attribute identified by
                // the given name only within the current node, it does NOT further the search in its JSONObject attributes.
                // Furthermore, retrieving the parent node with getJSONObject() is redundant as the parent node is already
                // at the top of the stack.
                //
                //Once the parent node is retrieved from the stack, the current node is added to it
                treeStack.peek().put(tempObject.getString("Groupname"), tempObject);
                treeStack.push(tempObject);
            } else if (treeStack.peek().getInt("Hierlevel") >= tempObject.getInt("Hierlevel")) {

//Getting rid of the nodes with the same level (the siblings)
                while (!treeStack.empty() && treeStack.peek().getInt("Hierlevel") >= tempObject.getInt("Hierlevel")) {
                    treeStack.pop();
                }

//Adding the current node to the parent node
                treeStack.peek().put(tempObject.getString("Groupname"), tempObject);
                treeStack.push(tempObject);
            }
        }

return new ResponseDTO(200, "ok", response);
    }

public static void main(String[] args) {
        JSONObject sapResponse = new JSONObject("{\n" +
                "  \"ControllingArea\" : \"TZUS\",\n" +
                "  \"TopNodes\" : false,\n" +
                "  \"Language\" : \"EN\",\n" +
                "  \"TONODES\" : [\n" +
                "    {\n" +
                "      \"Groupname\" : \"INC\",\n" +
                "      \"Hierlevel\" : 0,\n" +
                "      \"Valcount\" : 0,\n" +
                "      \"Descript\" : \"INC\"\n" +
                "    },\n" +
                "    {\n" +
                "      \"Groupname\" : \"INC-BBSR\",\n" +
                "      \"Hierlevel\" : 1,\n" +
                "      \"Valcount\" : 0,\n" +
                "      \"Descript\" : \"INC1\"\n" +
                "    },\n" +
                "    {\n" +
                "      \"Groupname\" : \"INC-STPI\",\n" +
                "      \"Hierlevel\" : 2,\n" +
                "      \"Valcount\" : 0,\n" +
                "      \"Descript\" : \"INC2\"\n" +
                "    },\n" +
                "    {\n" +
                "      \"Groupname\" : \"INC-FORT\",\n" +
                "      \"Hierlevel\" : 2,\n" +
                "      \"Valcount\" : 0,\n" +
                "      \"Descript\" : \"INC3\"\n" +
                "    },\n" +
                "    {\n" +
                "      \"Groupname\" : \"INC-BBL\",\n" +
                "      \"Hierlevel\" : 1,\n" +
                "      \"Valcount\" : 0,\n" +
                "      \"Descript\" : \"INC4\"\n" +
                "    },\n" +
                "    {\n" +
                "      \"Groupname\" : \"INC-PUNE\",\n" +
                "      \"Hierlevel\" : 1,\n" +
                "      \"Valcount\" : 0,\n" +
                "      \"Descript\" : \"INC5\"\n" +
                "    }\n" +
                "  ],\n" +
                "  \"TOVALUE\" : [\n" +
                "    {\n" +
                "      \"Valfrom\" : \"\",\n" +
                "      \"Valto\" : \"\"\n" +
                "    }\n" +
                "  ]\n" +
                "}");

JSONObject expectedJson = new JSONObject("{\n" +
                "    \"INC\": {\n" +
                "        \"Groupname\": \"INC\",\n" +
                "        \"Hierlevel\": 0,\n" +
                "        \"Valcount\": 0,\n" +
                "        \"Descript\": \"INC\",\n" +
                "        \"INC-BBSR\": {\n" +
                "            \"Groupname\": \"INC-BBSR\",\n" +
                "            \"Hierlevel\": 1,\n" +
                "            \"Valcount\": 0,\n" +
                "            \"Descript\": \"INC1\",\n" +
                "            \"INC-STPI\": {\n" +
                "                \"Groupname\": \"INC-STPI\",\n" +
                "                \"Hierlevel\": 2,\n" +
                "                \"Valcount\": 0,\n" +
                "                \"Descript\": \"INC2\"\n" +
                "            },\n" +
                "            \"INC-FORT\": {\n" +
                "                \"Groupname\": \"INC-FORT\",\n" +
                "                \"Hierlevel\": 2,\n" +
                "                \"Valcount\": 0,\n" +
                "                \"Descript\": \"INC3\"\n" +
                "            }\n" +
                "        },\n" +
                "        \"INC-BBL\": {\n" +
                "            \"Groupname\": \"INC-BBL\",\n" +
                "            \"Hierlevel\": 1,\n" +
                "            \"Valcount\": 0,\n" +
                "            \"Descript\": \"INC4\"\n" +
                "        },\n" +
                "        \"INC-PUNE\": {\n" +
                "            \"Groupname\": \"INC-PUNE\",\n" +
                "            \"Hierlevel\": 1,\n" +
                "            \"Valcount\": 0,\n" +
                "            \"Descript\": \"INC5\"\n" +
                "        }\n" +
                "    }\n" +
                "}");

ResponseDTO resp = getTreeStructure(sapResponse);

System.out.println(expectedJson);
        System.out.println();

System.out.println(resp.getResponse());
        System.out.println();

System.out.println(expectedJson.toString().equals(resp.getResponse().toString()));
    }

static class ResponseDTO {
        private int code;
        private String message;
        private JSONObject response;

public ResponseDTO(int code, String message, JSONObject response) {
            this.code = code;
            this.message = message;
            this.response = response;
        }

public int getCode() {
            return code;
        }

public void setCode(int code) {
            this.code = code;
        }

public String getMessage() {
            return message;
        }

public void setMessage(String message) {
            this.message = message;
        }

public JSONObject getResponse() {
            return response;
        }

public void setResponse(JSONObject response) {
            this.response = response;
        }
    }
}

STDIN

Output:

{"INC":{"Groupname":"INC","Descript":"INC","INC-BBSR":{"INC-FORT":{"Groupname":"INC-FORT","Descript":"INC3","Valcount":0,"Hierlevel":2},"Groupname":"INC-BBSR","Descript":"INC1","INC-STPI":{"Groupname":"INC-STPI","Descript":"INC2","Valcount":0,"Hierlevel":2},"Valcount":0,"Hierlevel":1},"Valcount":0,"INC-BBL":{"Groupname":"INC-BBL","Descript":"INC4","Valcount":0,"Hierlevel":1},"INC-PUNE":{"Groupname":"INC-PUNE","Descript":"INC5","Valcount":0,"Hierlevel":1},"Hierlevel":0}}

{"INC":{"Groupname":"INC","Descript":"INC","INC-BBSR":{"INC-FORT":{"Groupname":"INC-FORT","Descript":"INC3","Valcount":0,"Hierlevel":2},"Groupname":"INC-BBSR","Descript":"INC1","INC-STPI":{"Groupname":"INC-STPI","Descript":"INC2","Valcount":0,"Hierlevel":2},"Valcount":0,"Hierlevel":1},"Valcount":0,"INC-BBL":{"Groupname":"INC-BBL","Descript":"INC4","Valcount":0,"Hierlevel":1},"INC-PUNE":{"Groupname":"INC-PUNE","Descript":"INC5","Valcount":0,"Hierlevel":1},"Hierlevel":0}}

true