how to check if a button is clickable in java,selenium webdriver.ps:check if clickable not wait untill it is clickable

hey i am writing a test case in selenium, the test is based on a shopping website ( http://ift.tt/2aUbQIq ) and what i want to check in my test is if the size for the product select is available or not. the sizes that are not available are gred out on the website so i understand that they are not clickable anymore. I have tried using isEnabled and isDisplayed condition to check if its clickab;e but they don't work.

ps: i want to CHECK if its clickable so that my program can choose another size to carry on with the procedure (it is currently choosing randomly) so i don't want to wait for it to become clickable.