How to create JSON in alphabetical order by its KEY (Java)

Question

I'm getting JSON, but it's not in alphabetical order. How to sort json by it's KEY ? JSON:

{"b":"3","c":"1","a":"4"}

Expected output:

{"a":"4","b":"3","c":"1"}

Please help me to solve this problem. I really appreciate your help! Thanks!

Answer 1

You can use the jackson library.

First add a jackson to the maven dependency.

    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.8.7</version>
    </dependency>

Then use the code below.

    String jsonData = "{\"e\":\"6\",\"f\":\"1\",\"b\":\"3\",\"c\":\"1\",\"a\":\"4\"}";
    ObjectMapper om = new ObjectMapper();
    om.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);
    Map<String, Object> map = om.readValue(jsonData, HashMap.class);
    String json = om.writeValueAsString(map);
    System.out.println(json); // result : {"a":"4","b":"3","c":"1","e":"6","f":"1"}

When I test it, I get output in sorted form.

{"a":"4","b":"3","c":"1","e":"6","f":"1"}

Answer 2

So here is one of solution to sort JSON object by key alphabetically without using external libraries(for Android Studio). The sortedJSON is the one with key sorted alphabetically.

try{
        JSONObject jo = new JSONObject();
        
        jo.put("g", "9");
        jo.put("t", "8");
        jo.put("r", "7");
        jo.put("d", "6");
        jo.put("c", "5");
        jo.put("b", "4");
        jo.put("a", "1");

        Map<String, String> joToMap = new HashMap<>();

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

            joToMap.put(key, value.toString()); //since value is string so convert toString; depend on your value type
        }

        Map<String, String> sortedMap = new TreeMap<>(joToMap); //this will auto-sort by key alphabetically

        JSONObject sortedJSON = new JSONObject(); //recreate new JSON object for sorted result

        for (Map.Entry<String, String> entry : sortedMap.entrySet()) {
            sortedJSON.put(entry.getKey(), entry.getValue());
            // result will be {"a":"1","b":"4","c":"5","d":"6","g":"9","r":"7","t":"8"}
        }
    } catch (Exception e){
    } 

Answer 3

You can use maps for this purpose , then sort the map according to the map key. after that insert it into the JSON object. In your case declare the map as:

Map<String,Integer> mapName = new HashMap<>();