RestApi.setConfiguration(new RestApi.Config()
                .setScheme(RestApi.Config.HTTP)
                .setHost("api.host.com")
                .setPort(80)
                .setInitialRequirements(new InitialRequirements() {

                    //this check will be executed before every request
                    @Override
                    public void onCheckRequirements(Request<?> request) throws InitialRequirementsException {
                        if (!isOnline()){
                            throw new InitialRequirementsException("Offline!");
                        }
                    }
                })
                .setRestAuthorizationService(UserService.getInstance())
                .setTimeout(60000)
                .setLogLevel(Level.VERBOSE)
                .addHeader("lang", "en") //header that will be added to every request
                .setAuthorization("user", "pass123") //basic auth
                .setDeserializer(new JsonDeserializer(new JsonDeserializer.Config()
                        .setTimeInSeconds(true)))
                .setSerializer(new JsonSerializer(new JsonSerializer.Config()
                        .setTimeInSeconds(true)
                        .setIntBoolean(true)
                        .setSerializeNullValues(true)))
                .setErrorDeserializer(new JsonErrorDeserializer(new JsonErrorDeserializer.Config()
                        .setErrorClass(DefaultErrorResponse.class)))
                .setMockFactory(new CustomMockFactory())
        );

@JsonIgnoreProperties(ignoreUnknown = true)
public class Version {
    @JsonProperty("version_code")
    private int code;

    @JsonProperty("version_name")
    private String name;

    ...
}

public class SetVersion extends PostRequest<BooleanResponse> implements Authorizable {

    private final Version newVersion;

    public SetVersion(Version newVersion){
        this.newVersion = newVersion;
    }

    @Override
    protected void prepareRequest() {
        setUrlSegments("api", "version");

        putUrlParameter("user", "user");
        putParameter("version", newVersion);
    }
}

RestApi.execute(new SetVersion(version), new RequestListener<BooleanResponse>() {
    @Override
    public void onSuccess(BooleanResponse result) {
        Logger.debug("Success!!");
        Logger.debug(result);
    }

    @Override
    public void onFailed(RequestException e) {
        Logger.error(e);
    }
});

try {
    Version version = RestApi.executeSync(new GetVersion());
} catch (RequestException e) {
    Logger.error(e);
}

RestApi.pool(RestApi.SERIAL_EXECUTOR) //or RestApi.THREAD_POOL_EXECUTOR
        .add(new GetVersion(), 1)
        .add(new SetVersion(version), 2)
        .execute(new RequestPoolListener() {
            @Override
            public void onTaskSuccess(Object result, int requestCode) {
                //called for every request after sucessfully execution
            }

            @Override
            public void onSuccess(@NonNull Map<Integer, Object> result) {
                //called when all request finished succesfully or onFailed method returns false for failed executions
                //results can be obtained by the requestCodes from the 'result' map
            }

            @Override
            public boolean onFailed(RequestException e, int requestCode) {
                //called for every failed requests. If return true then all unfinished requests will be stopped and onSuccess method will not be invoked
                return false;
            }
        });

public class CustomMockFactory extends MockFactory {
    @Override
    public <T> T getMockResponse(Request<T> request) {
        if (BuildConfig.DEBUG) {
            if (request instanceof GetVersion) {
                return (T) getVersion();
            }
        }
        return null;
    }

    @NonNull
    private Version getVersion() {
        Version version = new Version();
        ApiVersion apiVersion = new ApiVersion();
        apiVersion.apiVersion = "1.0.0";
        apiVersion.expirationDate = Calendar.getInstance();
        apiVersion.expirationDate.setTimeInMillis(System.currentTimeMillis() + 100000);
        version.version = apiVersion;
        return version;
    }
}