Linked list clarification

In Java you have primitives (int, long, etc.) and objects. Objects are references (pointers) to complex data.

Java always passes values; so within your list you will have actual values of what you put in. BUT: Since objects are references to data, the values passed will be the references, not the data itself.

Pragmatic result: You put object A in a list and change its data somewhere in your code. Object A will still be in your list (you didn't change A but its data) but the A in your list will reflect the changes you've made somewhere else.

Car a = new Car();
List myList = new LinkedList();
myList.add(a);
a.driveHome();
Car carFromList = myList.getFirst();
carFromList.isDrivenHome(); // true

You can check out the OpenJDK LinkedList implementation on GrepCode. The LinkedList class itself contains a reference to an Entry named header, which contains references to two more Entry objects for the next and previous elements in the list.

To answer specifically: note that java.util.LinkedList defines a doubly-linked list.

The list has two member variables first and last that reference ("point at") the first and last nodes. List nodes are of type Entry<T>, where T is the type of the objects you are inserting.

Each list node or Entry thus contains:
T data : the actual item (object) inserted
Entry<T> next : a reference to ("pointing at") the next node (null if last)
Entry<T> previous : a reference to ("pointing at") the previous node (null if first)

For example, list (A,B,C,D) is represented as follows:

/   \  ->  /   \  ->  /   \  ->  /   \
| A |      | B |      | C |      | D |
\   /  <-  \   /  <-  \   /  <-  \   /
  ^                                ^
first                            last

• LinkedList uses index to store elements
• Elements are point(linked) to each other

There are 3 types of linked list

1.singly linked list = each node point the next node. (x)--->(y)--->(z)--->nothing

2.doubly linked list = each node point to next and previous node . (x)<-->(y)<-->(z)

3.circularly linked list. = each node point to next node (like singly-linked lists) last node and fist node linked (x)--->(y)--->(z)--->(x)