Radio buttons and checkboxes that are checked when the form that contains them is submitted will send a name/value pair to the server. Radio buttons and checkboxes that are unchecked will send nothing.
Form parameters are retrieved with the HttpServletRequest.getParameter(String) method; the String argument being the name. If the name argument doesn't match any form parameters, getParameter will return null.
This means that calling getParameter will return null if the radio button or checkbox is unchecked. If a checkbox or radio button is checked, then calling getParameter with that object's name will return a value.
When generating the HTML for a radio button or checkbox, adding the attribute "checked" will cause that button or checkbox to be checked.
We're pleased to have you here with us in the servlets forum, but there are a few rules that need to be followed, and one is that proper names are required. Please take a look at the JavaRanch Naming Policy and adjust your display name to match it.
In particular, your display name must be a first and a last name separated by a space character, and must not be obviously fictitious.