So to allow any type object I must use generics in my code.
I have rewrote this method to do so, but then when I create an object, for example Milk, it won't let me pass it to my method.
Ether there's something wrong with my generic revision, or Milk object I created is not good.
How should I pass my object correctly and add it to linked list?
This is a method that causes error when I insert an item:
public void insertFirst(T dd) // insert at front of list
{
Link newLink = new Link(dd); // make new link
if( isEmpty() ) // if empty list,
last = newLink; // newLink <-- last
else
first.previous = newLink; // newLink <-- old first
newLink.next = first; // newLink --> old first
first = newLink; // first --> newLink
}
This is my class I try to insert into linked list:
class Milk
{
String brand;
double size;
double price;
Milk(String a, double b, double c)
{
brand = a;
size = b;
price = c;
}
}
This is test method to insert the data:
public static void main(String[] args)
{ // make a new list
DoublyLinkedList theList = new DoublyLinkedList();
// this causes:
// The method insertFirst(Comparable) in the type DoublyLinkedList is not applicable for the arguments (Milk)
theList.insertFirst(new Milk("brand", 1, 2)); // insert at front
theList.displayForward(); // display list forward
theList.displayBackward(); // display list backward
} // end main()
} // end class DoublyLinkedApp
Declarations:
class Link<T extends Comparable<T>>
{}
class DoublyLinkedList<T extends Comparable<T>>
{}
