LinkedList of type that implements the comparable interface

Question

I'm looking for how to pass as a parameter of a method a linkedList of a type which implements the Comparable interface.

 public static void mergeSort(LinkedList<Comparable> list){}

I tried that but when I pass a primitive type such as Integer as a parameter it doesn't work. If someone have an idea?

Answer 1

You need to specify a bound parameter:

  public static <T extends Comparable<? super T>> void mergeSort(LinkedList<T> list){}

This is taken from the method sort .

Answer 2

Simply let the compiler know that the input type T extends Comparable<T> .

public static <T extends Comparable<T>> void mergeSort(final LinkedList<T> list)

I would not use the ? , which is a wildcard and represents an unknown type .
Explicitly specifying the generic type is always better (see this question ).

Answer 3

Define a type parameter, and use that type parameter as the element type:

public static <C extends Comparable<? super C>> void mergeSort(LinkedList<C> list){}