Yes, you can always use finalize as it's a public method in Object and since a method cannot be overwritten to have a stricter access modifier, you can always use it.
The real Question is: Do you want to? That answer is NO. This is because you could inadvertantly prevent the execution of other code provided by the container necessary for proper cleanup of the JSPs Super Classes and wind up with a lot of unnecessary Objects in your container everytime a JSP is redeployed. A good rule of Thumb is to only use the Super Class methods in JSPs (And most APIs) that the documentation tells you to.