Is an ArrayList the same thing as a singly-linked list?

Question

In Java, I have been asked to store integer values in a singly-linked list and then print the elements stored in the list. Here is what I came up with:

int max = 10;
List<Integer> list = new ArrayList<Integer>();

for (int num = 0; i < max; i++){
     list.add(num);
}
System.out.print(list);

I was wondering, is ArrayList the same thing as a singly-linked list? I want to make sure that I'm answering the question correctly. Does this make sense? Thanks!

Answer 1

No - ArrayList is not a linked list at all - it's an array list. ArrayList stores its elements in an array, whereas linked lists store them in arbitrary memory by linking objects together.

LinkedList is a doubly-linked list, and I'm sure that there are various singly linked list implementations you could grab, but given that this is an assignment you'll either be marked down or fail outright if you try to hand in code using someone else's implementation.

Instead, find an article etc. which describes linked lists and try to implement one yourself.

Generally these are built in java by having a class SomeClass containing a forward link of type SomeClass and a value. You build the list by linking each SomeClass instance to the next through the forward link.

Answer 2

No ArrayList is definitely not the same as a singly linked list. In fact, it is not a linked list at all: it is a list that uses an array for its backing storage. This lets you access ArrayList in arbitrary order, as opposed to linked lists, that must be accessed sequentially.

Java library has a doubly-linked list, but no singly-linked one; you need to write it yourself.

There are several good implementations available on the internet; take a look at this answer on the codereview site to gain some ideas on how to implement a singly linked list of your own.