Java Method using generic parameter?

I am inferring that you are writing your own linked list and that your declaration looks something like this:

class MyLinkedList<T> {
  …

If so, the <T> means that your class has a generic type variable, T, that represents the type of the list's elements.

Given that, the insert method could look something like this:

void insertList(List<? extends T> list, int index) {
  /* Count links to find the insertion point */
  /* Remember the link that used to follow */
  …
  for(T obj : list) {
    /* Create link for obj and link it to previous */
    /* Update previous */
    …
  }
  /* Attach the old link you remembered to previous */
  …
}

Here, ? extends T means that you accept anything that extends the generic type of your list.

There's no need to require the collection of inserted elements to be MyLinkedList, or even List—it could be any type of collection that you could iterate.

For what I understand you have sue that the object passed to the function will be a LinkedList, even if you did not know you could make use of 'instanceof' to test if the object is an instance of some type, after you can make use of "cast" resources to "transform" an generic object to another type. Se the code bellow and adapt for your use.

    public static void main(String[] args) {


        List<Banana> lista = new LinkedList<Banana>();
        testingAndCastingSomeObject(lista);

    }

    /**
     * This method will receive a generic object and test if it is a LinkedList, if it is it will cast the object "transforming" it in a LinkedList
     * Afte this I can make what I want
     * @param object
     */
    static void testingAndCastingSomeObject(Object object) {
        LinkedList<?> test = null;
        if(object instanceof LinkedList<?>) {
            test = (LinkedList<?>) object;
        }

        //If the List is not empty and the first objetct is a Banana I can cast it too
        if(!test.isEmpty() && test.get(0) instanceof Banana ) {

            Banana banana = (Banana) test.get(0);
            System.out.println("Here is my banana: " +banana);

        }

    }

    public class Banana{
        //Banana members and methods
    }