Java: How to refer to a class inside the class but of another element?

I'm not to sure on how to explain this but basically I am trying to refer to the List Classes front which is of Element A(can be from any list). But what happens is that when it goes through the Elements of the list it is comparing from two different lists and ends up not matching. ie compares original list which contains the front b to list containing element A. Now I'm just wondering about how i would get the front of Element A set to b so that i can compare where it is.

/*front is a dummy element used to keep position.
List is a class i have made under requirements of naming for subject.
i don't want a solution. I only want to know about how to do it.

This is what is an example code of whats causing the problem USED IN DRIVER PROGRAM
DLL.concat(DLL2);
it is basically getting DLL's front and going through the loop when it should be using DLL2's.

DLL and DLL2 are both Lists
***/


    //will return the index of the Element for comparing

    private int checkElement(Element A){

        Element b = front;

            int i = 0;  
            while (b != a && i<size)
            {
                b = b.next;
                i++;
            }

            return i;
        }


//edit: add

//size is the size of the list gets increased everytime a var开发者_如何转开发iable is added to the list on top of the dummy element.

//Item is a private class inside the List class. it contains the values: element,next, previous in which element contains an object, next and previous contain the next element in the list and the previous one (its a double linked list) 

// this is what causes the error to turn up in the above method as im using two different lists and joining them.

    public void concat(List L){
        if  (splice(L.first(),L.last(),last())){
            size = size+L.size;
        }
    }

//this is the splice method for cutting out elements and attaching them after t
//just using the check method to assert that a<b and will later use it to assert t not inbetween a and b

public boolean splice(Element a, Element b, Element t){

        if  (checkElement(a) < checkElement(b)){

            Element A = a.previous;
            Element B = b.next;
            A.next = B;
            B.previous = A;

            Element T = t.next;

            b.next = T;
            a.previous = t;
            t.next = a;
            T.previous = b;
        return true;
        }
        else {

        System.out.println("Splicing did not occur due to b<a");        
        return false;
        }

    }

So despite my comment, I see one glaring problem with this. You can't use equality operators on reference types. That is, anything other than a primitive type (double, int, etc). What happens is you're comparing the address of the instance and unless they are literally the same object (same address in memory), it isn't going to return true, ever. Maybe that's what you want, but I suspect not. You need to override the method

public boolean equals(Object obj);

and use that to compare two instances of a given class. Am I correct in my assumptions?

Edit Ok, I think my original guess was correct. It works if they are from the same list because they end up being the same elements (stored in the same memory location). You need to use equals() or !equals() rather than == and !=. Try that, and see if it solves your problems. Also, don't just use them, you must override equals to actually compare the elements internal properties.