Java reflection - get primitive class value from java variable

I am trying to execute methods of a class using reflection, the method accepts a map of methodNames & list of arguments the method needs. One such method is setPaperSize(int x). Now the problem is at the //error line, x.getClass() returns Integer not int, and due to that I end up with NoSuchMethodException. I know this returns runtime class of variables, Any workarounds or solutions to make it work?

private void applyProps(HTML2PDF converter, Map<String, Object> propValues) {
        propValues.keySet().forEach(k -> {
            Method methodToExecute;
            try {
                Object argObj = propValues.get(k);
                List<Object> args = null;
                if(argObj instanceof List) {
                    args = (List<Object>)argObj;
                }else {
                    args = new ArrayList<Object>();
                    args.add(argObj);
                }               
//error line
                List<Class<?>> argsClass =  args.stream().map(x -> x.getClass()).collect(Collectors.toList());
                methodToExecute = HTML2PDF.class.getMethod(k, argsClass.toArray(new Class[argsClass.size()]));              
                methodToExecute.invoke(converter, args);
            } catch (NoSuchMethodException | SecurityException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
                throw new RuntimeException("Error in invoking the reflection method", e);
            }
        });
    }