How to Convert a JSON String to a HashMap in Java?

Converting JSON String to a HashMap with Java

In Java, parsing JSON data and storing it in a HashMap can be achieved using various techniques. Here's how you can do it using the org.json library:

public static Map<String, Object> jsonToMap(JSONObject json) throws JSONException {
    Map<String, Object> retMap = new HashMap<>();

    if (json != JSONObject.NULL) {
        retMap = toMap(json);
    }
    return retMap;
}

public static Map<String, Object> toMap(JSONObject object) throws JSONException {
    Map<String, Object> map = new HashMap<>();

    Iterator<String> keysItr = object.keys();
    while (keysItr.hasNext()) {
        String key = keysItr.next();
        Object value = object.get(key);

        if (value instanceof JSONArray) {
            value = toList((JSONArray) value);
        } else if (value instanceof JSONObject) {
            value = toMap((JSONObject) value);
        }
        map.put(key, value);
    }
    return map;
}

public static List<Object> toList(JSONArray array) throws JSONException {
    List<Object> list = new ArrayList<>();
    for (int i = 0; i < array.length(); i++) {
        Object value = array.get(i);
        if (value instanceof JSONArray) {
            value = toList((JSONArray) value);
        } else if (value instanceof JSONObject) {
            value = toMap((JSONObject) value);
        }
        list.add(value);
    }
    return list;
}

To use this method, instantiate a JSONObject object from your JSON String, then pass it as an argument to the jsonToMap method. It will recursively parse the JSON structure and convert it into a HashMap.

Alternatively, you can use the Jackson library for a more concise solution:

import com.fasterxml.jackson.databind.ObjectMapper;

Map<String, Object> mapping = new ObjectMapper().readValue(jsonStr, HashMap.class);

Simply replace jsonStr with your actual JSON String.

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