Example.java

new JsonBuilder<String, String>()
    .put("$email", "mail@google.com")
    .put("$username", "username")
    .put("$name", "Name Name")
    .build()

JsonBuilder.java

package com.utils;

import org.json.JSONObject;

import java.util.HashMap;
import java.util.Map;

import timber.log.Timber;

public class JsonBuilder<K, V> {
    private final Map<K, V> map = new HashMap<>();

    public JsonBuilder<K, V> put(K key, V value) {
        if (key != null && value != null) {
            map.put(key, value);
        }
        return this;
    }

    public JSONObject build() {
        return new JSONObject(map);
    }
}