Easy mock factory

public class LogicFactory {

    // Check for test mode
    private static boolean isTestMode = false;
    private static boolean canChangeMode = true;

    private LogicFactory(){
        // Empty constructor for readability. Class will only contain static methods
    }

    public static void setTestMode(boolean isTestMode){
        if(LogicFactory.canChangeMode) {
            LogicFactory.isTestMode = isTestMode;
            canChangeMode = false;
        }
        else
            throw new IllegalStateException("Logic factory state already has been defined and can only be defined once");
    }


    public static IMessageCreator createMessageCreator(){
        if(isTestMode)
            return new MessageCreatorMock();
        else
            return new MessageCreator();
    }