if you can separate your code from the GPL in such a way that the GPL version becomes only a lib (unmodified), then you can close or do any licensing you like.

for example.

package com.mycompany.lib

import org.someGPL.lib.A;

myClass B extends A {}

In this case you simply include the GPL lib as GPL and your Lib as any type of license

in your class B you can override functions you don't like and add more of your own functions.

Finally when you release your code you have to say that this code uses the following GPL code...