Java – Linked list clarification

javalinked list

This is a pretty simple question but I'm new to java.

The linked list found in java.util.LinkedList.

I saw elsewhere that Java does not use pointers…

When I create a new list and add new elements to it, does the list contain references to the data and to the next/previous elements or does it also contain the object itself.

Best Answer

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

Related Solutions

Does the Head(start) pointer of Doubly Linked list points previously to the tail(last) node

It depends.

Is it a circular or linear list?

If it's a circular list then there is no "head" or "tail" as each element's next and prev pointers will be set. You can start traversing the list anywhere and have to remember where you started so you know when to stop.

If it's a linear list then the prev pointer of the head element will be null and the next pointer of the tail element will be null. You use this information to know when to stop.

C++ – 2D linked list vs. multidimensional array/vector

I hope it's ok to answer my own question. I believe I have found the optimal (without overcomplicating the problem) data structure for my problem. There was at least minor idiocy on my part for not recognising this earlier. The data doesn't need to be accessed by (x,y,z) but instead by (x, y, range of z (say 0 - 3)). This give a C++ struct as follows:

struct node {
  struct node *next;
  int zGroup;
  int z;
  50 bytes of misc data };

I can then address this through a 3D dynamic array (vectors):

vector< vector < vector < node* > > > Data;

Any given Data[x][y][zGroup] points to the first element of a linked list, the entirety of which is needed every time one element of it is needed. No value of this array is NULL, every one contains a linked-list of at least one element.

The third dimension of the array - the zGroup has jagged dimensions, but with dynamic arrays this isn't an issue. Given the data and computations being performed on it, I know that the max x and y values are set when the file is read and do not change, neither does the number of z groups on any given (x,y) line, the actual z-values of nodes may change, but they will remain inside the same z-groups, giving a constant-sized, fully populated array.

With the way that the file is structured it is also easy enough to page it in and out of memory if I am brought to do this with much larger data sets.

Best Answer

Related Solutions

Does the Head(start) pointer of Doubly Linked list points previously to the tail(last) node

C++ – 2D linked list vs. multidimensional array/vector

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