Volley request class with support for array values in payload

Request.java

import com.android.volley.AuthFailureError;

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;
 
/**
 * Volley request class with support for array values in payload
 */
public class Request<T> extends com.android.volley.Request<T> {
    private static final String ARRAY_PARAM = "%s[]";

    /**
     * Returns custom body payload with support for array params
     * If not empty, this payload will be used in favor to one returned by {@link #getParams()}
     * @return an instance of {@link Request.RequestParams}
     * @see #getParams()
     * @see #getBody()
     */
    protected RequestParams getPayload() {
        return null;
    }

    @Override
    public byte[] getBody() throws AuthFailureError {
        // if no custom payload specified, we fallback to default getBody()
        RequestParams payload = getPayload();
        if (payload == null || payload.isEmpty()) {
            return super.getBody();
        }

        StringBuilder encodedParams = new StringBuilder();
        String paramsEncoding = getParamsEncoding();
        try {
            Map<String, String> stringParams = payload.stringParams;
            for (Map.Entry<String, String> entry : stringParams.entrySet()) {
                encodedParams.append(URLEncoder.encode(entry.getKey(), paramsEncoding));
                encodedParams.append('=');
                encodedParams.append(URLEncoder.encode(entry.getValue(), paramsEncoding));
                encodedParams.append('&');
            }

            Map<String, Iterable<String>> arrayParams = payload.arrayParams;
            for (Map.Entry<String, Iterable<String>> entry : arrayParams.entrySet()) {
                for (String value : entry.getValue()) {
                    encodedParams.append(URLEncoder.encode(entry.getKey(), paramsEncoding));
                    encodedParams.append('=');
                    encodedParams.append(URLEncoder.encode(value, paramsEncoding));
                    encodedParams.append('&');
                }
            }
            return encodedParams.toString().getBytes(paramsEncoding);
        } catch (UnsupportedEncodingException uee) {
            throw new RuntimeException("Encoding not supported: " + paramsEncoding, uee);
        }
    }

    /**
     * Custom payload with support for array params
     */
    public static class RequestParams {
        private final Map<String, String> stringParams = new HashMap<>();
        private final Map<String, Iterable<String>> arrayParams = new HashMap<>();

        /**
         * Set string param
         * @param key   param key
         * @param value param value
         */
        public void put(String key, String value) {
            stringParams.put(key, value);
        }

        /**
         * Set array param
         * @param key       param key
         * @param values    param values
         */
        public void put (String key, Iterable<String> values) {
            arrayParams.put(String.format(ARRAY_PARAM, key), values);
        }

        private boolean isEmpty() {
            return stringParams.isEmpty() && arrayParams.isEmpty();
        }
    }
}

thank you